Formation and metabolism of pungent principle of Capsicum fruits. XV. Microdetermination of capsaicin by high-performance liquid chromatography with electrochemical detection

Targeting lipid droplets and lipid droplet-associated proteins: a new perspective on natural compounds against metabolic diseases

BACKGROUND

Lipid droplet (LD) is a metabolically active organelle, which changes dynamically with the metabolic state and energy requirements of cells. Proteins that either insert into the LD phospholipid monolayer or are present in the cytoplasm, playing a crucial role in lipid homeostasis and signaling regulation, are known as LD-associated proteins.

METHODS

The keywords "lipid droplets" and "metabolic diseases" were used to obtain literature on LD metabolism and pathological mechanism. After searching databases including Scopus, OVID, Web of Science, and PubMed from 2013 to 2024 using terms like "lipid droplets", "lipid droplet-associated proteins", "fatty liver disease", "diabetes", "diabetic kidney disease", "obesity", "atherosclerosis", "hyperlipidemia", "natural drug monomers" and "natural compounds", the most common natural compounds were identified in about 954 articles. Eventually, a total of 91 studies of 10 natural compounds reporting in vitro or in vivo studies were refined and summarized.

RESULTS

The most frequently used natural compounds include Berberine, Mangostin, Capsaicin, Caffeine, Genistein, Epigallocatechin-3-gallate, Chlorogenic acid, Betaine, Ginsenoside, Resveratrol. These natural compounds interact with LD-associated proteins and help ameliorate abnormal LDs in various metabolic diseases.

CONCLUSION

Natural compounds involved in the regulation of LDs and LD-associated proteins hold promise for treating metabolic diseases. Further research into these interactions may lead to new therapeutic applications.

Future targets for migraine treatment beyond CGRP

BACKGROUND

Migraine is a disabling and chronic neurovascular headache disorder. Trigeminal vascular activation and release of calcitonin gene-related peptide (CGRP) play a pivotal role in the pathogenesis of migraine. This knowledge has led to the development of CGRP(-receptor) therapies. Yet, a substantial proportion of patients do not respond to these treatments. Therefore, alternative targets for future therapies are warranted. The current narrative review provides a comprehensive overview of the pathophysiological role of these possible non-CGRP targets in migraine.

FINDINGS

We covered targets of the metabotropic receptors (pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal peptide (VIP), amylin, and adrenomedullin), intracellular targets (nitric oxide (NO), phosphodiesterase-3 (PDE3) and -5 (PDE5)), and ion channels (potassium, calcium, transient receptor potential (TRP), and acid-sensing ion channels (ASIC)). The majority of non-CGRP targets were able to induce migraine-like attacks, except for (i) calcium channels, as it is not yet possible to directly target channels to elucidate their precise involvement in migraine; (ii) TRP channels, activation of which can induce non-migraine headache; and (iii) ASICs, as their potential in inducing migraine attacks has not been investigated thus far. Drugs that target its receptors exist for PACAP, NO, and the potassium, TRP, and ASIC channels. No selective drugs exist for the other targets, however, some existing (migraine) treatments appear to indirectly antagonize responses to amylin, adrenomedullin, and calcium channels. Drugs against PACAP, NO, potassium channels, TRP channels, and only a PAC₁ antibody have been tested for migraine treatment, albeit with ambiguous results.

CONCLUSION

While current research on these non-CGRP drug targets has not yet led to the development of efficacious therapies, human provocation studies using these targets have provided valuable insight into underlying mechanisms of migraine headaches and auras. Further studies are needed on these alternative therapies in non-responders of CGRP(-receptor) targeted therapies with the ultimate aim to pave the way towards a headache-free future for all migraine patients.

Fully nondestructive analysis of capsaicinoids electrochemistry data with deep neural network enables portable system

Electrochemical methods have been extensively applied for the detection of chemical information from food or other analytes. However, existing electrochemical methods are limited to focusing solely on the absorption peaks and disregard much of the hidden chemical fingerprint information. Consequently, electrochemical sensors are constrained by their ability to detect samples containing multiple source-material mixtures with overlapping constituents. We hypothesized that the target substances can be effectively identified and detected using differential sensor data combined with artificial intelligence (AI). In this study, we developed a novel signal array composed of five metal electrodes and used a convolutional neural network (CNN) model for feature extraction to detect capsaicinoids in stews. Our results indicate that the proposed method achieved satisfactory predictions with a root mean square error (RMSE) of 5.407 in independent brine samples. This provides a promising strategy and practical approach for the nondestructive analysis of multidimensional electrochemical data of mixed analytes.

Bioavailability of a Capsaicin Lipid Multi-particulate Formulation in Rats

Background and Objective

Because of the stomach-burning sensation it induces, capsaicin has been used at relatively low doses as a nutritional supplement, which has limited its bioavailability. The objective of this study was to investigate the serum bioavailability of capsaicin supplementation with or without a lipid multi-particulate (LMP) formulation.

Methods

Thirty-five rats were divided into five groups and administered capsaicin at either 0.2 or 1 mg/kg with or without the LMP formulation. Capsaicin bioavailability was assessed based on the area under the concentation–time curve (AUC), the time to peak concentration (T_max), and the peak serum concentration (C_max).

Results

For each formulation, the capsaicin C_max was reached at 90 min and decreased thereafter. Serum capsaicin concentrations were greater in rats administered the higher dose of capsaicin (1 mg/kg) in the LMP formulation at all measurement times (P  ≤ 0.05). The AUC showed a significant increase, about 20%, when capsaicin was administered in the LMP formulation at the high dose (P  = 0.002). The T_max for oral capsaicin was similar whether or not administration was via the LMP formulation (P  = 0.163). However, the C_max of capsaicin increased in a dose-dependent manner (P  < 0.05). Although the LMP formulation of the high dose of capsaicin resulted in a numerically higher C_max, it was not statistically significantly higher (P  = 0.068).

Conclusions

The present work demonstrated that administration of capsaicin via the LMP formulation significantly impacted the pharmacokinetic parameters and the serum bioavailability of orally administered 1 mg/kg capsaicin in rats. The bioavailability of capsaicin in humans may also be increased by using the LMP formulation.

Electroanalytical overview: the pungency of chile and chilli products determined via the sensing of capsaicinoids

When you bite into a chile pepper or eat food containing chile (chilli), one might feel heat, or other associated feelings, some good such as the release of endorphins, and some bad. The heat, or pungency, and related feelings from eating chile peppers are the result of their chemical composition, i.e. the concentrations of capsaicinoids. The major components are capsaicin and dihydrocapsaicin, which occur in chiles in the ratio of 6 : 4. Other capsaicinoids occur in smaller concentrations and are known as the "minor" capsaicinoids. Wilbur L. Scoville in 1912 created an organoleptic test, now known as the Scoville scale, which asked a panel of tasters to state when an increasingly dilute solution of the chile pepper in alcohol no longer burned the mouth. Following the Scoville scale, a plethora of analytical techniques later followed. In this overview, we explore the endeavours directed to the development of electrochemical-based sensors for the determination of capsaicin and related compounds, starting from their use in hyphenated laboratory set-ups to their modern use as stand-alone electroanalytical sensors. The latter have the advantage of providing a rapid and sensitive methodology that has the potential to be translated in the field; future trends and issues to be overcome are consequently suggested.

Dispersive liquid-liquid microextraction for the isolation and HPLC-DAD determination of three major capsaicinoids in Capsicum annuum L

Dispersive liquid-liquid microextraction (DLLME) was combined with high-performance liquid chromatography-diode-array detector (HPLC-DAD) for the extraction and quantitation of three major capsaicinoids (i.e. capsaicin, dihydrocapsaicin and nordihydrocapsaicin) from pepper (Capsicum annuum L.). Chloroform (extraction solvent, 100 μL), acetonitrile (disperser solvent, 1250 μL) and 30 s extraction time were found optimum. The analytes were back-extracted into 300 μL of 50 mM sodium hydroxide/ methanol, 45/55% (v/v), within 15 s before being injected into the instrument. Enrichment factors ranged from 3.3 to 14.7 and limits of detection from 5.0 to 15.0 µg g-1. Coefficients of determination (R2) and %RSD were higher than 0.9962 and lower than 7.5%, respectively. The proposed method was efficiently applied for the extraction and quantitation of the three capsaicinoids in six cultivars of Capsicum annuum L. with percentage relative recoveries in the range of 92.0%-108.0%. DLLME was also scaled up for the isolation of the three major capsaicinoids providing purity greater than 98.0% as confirmed by liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) analysis, which significantly reduced the extraction time and organic solvent consumption.

Novel Agents in Neuropathic Pain, the Role of Capsaicin: Pharmacology, Efficacy, Side Effects, Different Preparations

PURPOSE OF REVIEW

Capsaicin is a natural substance used to treat neuropathic pain because of its ability to be used in a more direct form on patients and efficiently treat their pain without the amount of side effects seen in the use of oral medications.

RECENT FINDINGS

Currently, the treatments for neuropathic pain are, control of the underlying disease process, then focused on symptomatic relief with pharmacotherapy, topical analgesics, or other interventions. When all pharmacological agents fail to relieve the pain, interventional strategies can be considered, such as neural blocks, spinal cord stimulation, and intrathecal administered medications. The response to current treatment of neuropathic pain is only modest relief of symptoms. Multiple treatment options may be attempted, while ultimately leaving patients with refractory neuropathic pain. For these reasons, a better treatment approach to neuropathic pain is greatly needed. Overall, capsaicin has great potential for becoming a first- or second-line treatment for neuropathic pain, and for becoming a therapeutic option for many other neuropathic pain-related disease states.

Utility of in vitro and in vivo systems for studying the permeability of capsaicin and nonivamide through different intestinal regions

1. The present study determined and compared the permeability of capsaicin and nonivamide along the length of the intestine in rats. Accordingly, the purpose was to evaluate this synthetic analog as a clinical substitute for capsaicin.. 2. Permeabilities of capsaicin and nonivamide were measured in experiments utilizing Ussing chambers and in vivo methods. Capsaicin concentrations were examined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). 3. Both capsaicin (0.80 × 10^-6cm/s) and nonivamide (0.22 × 10^-6cm/s, p > 0.05) had poor permeabilities across the jejunal membrane. The permeability of nonivamide (10.12 × 10^-6cm/s) was significantly greater than that of capsaicin (5.34 × 10^-6cm/s, p < 0.05) across the iliac membrane. In contrast, the permeability of nonivamide (8.42 × 10^-6cm/s) across the colonic membrane was markedly lower than that of capsaicin (14.48 × 10^-6cm/s, p < 0.05). In accordance with the in vitro study, the drug concentration-time curve of nonivamide was significantly higher in the ileum (F = 14.18, p < 0.05) but lower in the colon (F = 11.86, p < 0.05) compared with capsaicin. 4. The results demonstrate that capsaicin and nonivamide exhibit varying permeabilities across several different intestinal tissues. The relevance of such extended investigations to healthcare is underscored by the lower cost of nonivamide versus capsaicin, along with potential application in prevention and management of the disease.

Influence of water stresses on capsaicinoid production in hot pepper (Capsicum chinense Jacq.) cultivars with different pungency levels

Although water stress reduces fruit yield, it also increases capsaicinoid accumulation in hot pepper. The aim of this study was to investigate the effect of different water regimes on capsaicinoid production in Capsicum chinense Jacq. having different pungency levels. Four hot pepper (C. chinense) cultivars were planted with four water regimes after anthesis: daily irrigation (control; S1), every 2 days (S2), every 3 days (S3) and every 4 days (S4). The results found that Akanee Pirote with the S2 treatment gave the highest capsaicinoid yield, and the increase of capsaicinoid yield was attributed from increasing the absolute capsaicinoid content and reducing the dry fruit yield as compared to the control. Capsaicinoid yield of Bhut Jolokia, Orange Habanero, and BGH1719 responded to the water stresses, but produced less capsaicinoid yield as compared to the control. This study reveals that appropriate water stress could increase capsaicinoid yield in some, but not all, hot pepper cultivars.

Development of a HPLC Method for the Quantitative Determination of Capsaicin in Collagen Sponge

Controlling the concentration of drugs in pharmaceutical products is essential to patient's safety. In this study, a simple and sensitive HPLC method is developed to quantitatively analyze capsaicin in collagen sponge. The capsaicin from sponge was extracted for 30 min with ultrasonic wave extraction technique and methanol was used as solvent. The chromatographic method was performed by using isocratic system composed of acetonitrile-water (70 : 30) with a flow rate of 1 mL/min and the detection wavelength was at 280 nm. Capsaicin can be successfully separated with good linearity (the regression equation is A = 9.7182C + 0.8547; R (2) = 1.0) and perfect recovery (99.72%). The mean capsaicin concentration in collagen sponge was 49.32 mg/g (RSD = 1.30%; n = 3). In conclusion, the ultrasonic wave extraction method is simple and the extracting efficiency is high. The HPLC assay has excellent sensitivity and specificity and is a convenient method for capsaicin detection in collagen sponge. This paper firstly discusses the quantitative analysis of capsaicin in collagen sponge.

Capsaicin induces apoptosis in human small cell lung cancer via the TRPV6 receptor and the calpain pathway

Capsaicin, the pungent ingredient of chili peppers, displays potent anti-neoplastic activity in a wide array of human cancer cells. The present manuscript examines the signaling pathways underlying the apoptotic activity of capsaicin in human small cell lung cancer (SCLC) in vitro and in vivo. Studies in neuronal cells show that capsaicin exerts its biological activity via the transient receptor potential vanilloid (TRPV) superfamily of cation-channel receptors. The TRPV family is comprised of six members (TRPV1-6). Capsaicin is a known agonist of the TRPV1 receptor. We observed that capsaicin-induced apoptosis in human SCLC cells was mediated via the TRPV receptor family; however it was independent of TRPV1. Surprisingly, the apoptotic activity of capsaicin required the TRPV6 receptor. Depletion of TRPV6 receptor by siRNA methodology abolished the apoptotic activity of capsaicin in SCLC cells. Immunostaining and ELISA showed that TRPV6 receptor was robustly expressed on human SCLC tissues (from patients) and SCLC cell lines but almost absent in normal lung tissues. This correlates with our results that capsaicin induced very little apoptosis in normal lung epithelial cells. The pro-apoptotic activity of capsaicin was mediated by the intracellular calcium and calpain pathway. The treatment of human SCLC cells with capsaicin increased the activity of calpain 1 and 2 by threefold relative to untreated SCLC cells. Such calpain activation, in response to capsaicin, was downstream of the TRPV6 receptor. Taken together, our data provide insights into the mechanism underlying the apoptotic activity of capsaicin in human SCLCs.

Bioavailability of capsaicin and its implications for drug delivery

The dietary compound capsaicin is responsible for the "hot and spicy" taste of chili peppers and pepper extracts. It is a valuable pharmacological agent with several therapeutic applications in controlling pain and inflammation. Emerging studies show that it displays potent anti-tumor activity in several human cancers. On a more basic research level, capsaicin has been used as a ligand to activate several types of ion-channel receptors. The pharmacological activity of capsaicin-like compounds is dependent on several factors like the dose, the route of administration and most importantly on its concentration at target tissues. The present review describes the current knowledge involving the metabolism and bioavailability of capsaicinoids in rodents and humans. Novel drug delivery strategies used to improve the bioavailability and therapeutic index of capsaicin are discussed in detail. The generation of novel capsaicin-mimetics and improved drug delivery methods will foster the hope of innovative applications of capsaicin in human disease.

Improved oral bioavailability of capsaicin via liposomal nanoformulation: preparation, in vitro drug release and pharmacokinetics in rats

This study innovatively prepared an effective capsaicin-loaded liposome, a nanoformulation with fewer irritants, for oral administration. The in vitro and in vivo properties of the liposomal encapsulation were investigated and the potential possibility of oral administration evaluated. The liposomal agent composed of phospholipid, cholesterol, sodium cholate and isopropyl myristate was prepared using film-dispersion method. A level A in vitro-in vivo correlation (IVIVC) was established for the first time, which demonstrated an excellent IVIVC of both formulated and free capsaicin in oral administration. Physicochemical characterizations including mean particle size, zeta (ζ) potential and average encapsulation efficiency of capsaicin-loaded liposome were found to be 52.2 ± 1.3 nm, -41.5 ± 2.71 mv and 81.9 ± 2.43 %, respectively. In vivo, liposomal encapsulation allowed a 3.34-fold increase in relative bioavailability compared to free capsaicin. The gastric mucosa irritation studies indicated that the liposomal system was a safe carrier for oral administration. These results support the fact that capsaicin, an effective drug for the treatment of neuropathic pain, could be encapsulated in liposome for improved oral bioavailability. The excellent IVIVC of capsaicin-loaded liposome could also be a promising tool in liposomal formulation development with an added advantage of reduced animal testing.

Electrochemical evaluation and adsorptive stripping voltammetric determination of capsaicin or dihydrocapsaicin on a disposable pencil graphite electrode

Capsaicin and dihydrocapsaicin are the two most abundant capsaicinoids in peppers, which are responsible for about 90% of the spiciness. A detailed study of the electrochemical properties of these compounds at pencil graphite (PG) electrode was carried out in the pH range 1.0-12.0 in aqueous solutions. The compounds underwent irreversible oxidation at PG electrode, which was an adsorption-controlled process with two protons and two electrons. The voltammetric data indicated that their oxidation proceeded via an ECE mechanism. Using the square-wave adsorptive stripping voltammetry with accumulation at a fixed potential of -0.1V for 120s, both of them yielded a well-defined voltammetric response at +0.31V (vs. Ag/AgCl) in Britton-Robinson buffer, pH 9.0. Capsaicin and dihydrocapsaicin could be determined with detection limits of 1.12 ng mL(-1) (3.7×10(-9)M) and 0.28 ng mL(-1) (9.1×10(-10)M), respectively. The practical applicability of this methodology was tested in commercial Turkish pepper products. The concentration of total capsaicinoids was determined using capsaicin as standard.

Design and in vitro evaluation of capsaicin transdermal controlled release cubic phase gels

The purpose of this study was to design and investigate the transdermal controlled release cubic phase gels containing capsaicin using glycerol monooleate (MO), propylene glycol (1,2-propanediol, PG), and water. Three types of cubic phase gels were designed based on the ternary phase diagram of the MO-PG-water system, and their internal structures were confirmed by polarizing light microscopy (PLM) and small-angle X-ray scattering (SAXS). Release results showed the cubic phase gels could provide a sustained system for capsaicin, while the initial water content in the gels was the major factor affecting the release rate. Release kinetics was determined to fit Higuchi's square-root equation indicating that the release was under diffusion control. The calculated diffusion exponent showed the release from cubic phase gels was anomalous transport. The unique structure of the cubic phases, capsaicin distributed in the lipid bilayers, and cubic phase gel swelling contributed to the release mechanism. The cubic phase gel may be an interesting application for transdermal delivery system of capsaicin in alleviating the post-incision pain.

Effect of HPbetaCD on solubility and transdermal delivery of capsaicin through rat skin

We evaluated the ability of hydroxypropyl-beta-cyclodextrin (HPbetaCD) to influence the percutaneous absorption of capsaicin (CP) through isolated rat skin. Phase solubility analysis and phase distribution studies suggested the potential of HPbetaCD as a solubilizer and permeation enhancer for CP. In vitro permeation studies showed the trend that, the penetration flux (J(s)) of CP increased with the increasing concentration of HPbetaCD from 0 to 2.20% (w/v), and then decreased dramatically when the concentration of HPbetaCD kept on increasing up to 15% (w/v). 2.20% (w/v) of HPbetaCD provided both just adequate solubilization and preferred J(s) for the permeation of CP (0.075%, w/v). Similar change patterns of the permeation parameters were also observed in the hydrogels, but the J(s) of CP was reduced significantly along with the increasing concentration of Carbopol U21. Histological analysis showed an invasive action of HPbetaCD on the stratum corneum (SC) of rat skin, which could only reduce the lag time (T(L)) but could not increase the J(s) of CP. On the other hand, the complexation of HPbetaCD with CP could attenuate this invasive action. It is inferred that excess of HPbetaCD could not only disturb the percutaneous absorption of CP but also disrupt the structure of SC.

Final report on the safety assessment of capsicum annuum extract, capsicum annuum fruit extract, capsicum annuum resin, capsicum annuum fruit powder, capsicum frutescens fruit, capsicum frutescens fruit extract, capsicum frutescens resin, and capsaicin

Capsicum-derived ingredients function as skin-conditioning agents--miscellaneous, external analgesics, flavoring agents, or fragrance components in cosmetics. These ingredients are used in 19 cosmetic products at concentrations as high as 5%. Cosmetic-grade material may be extracted using hexane, ethanol, or vegetable oil and contain the full range of phytocompounds that are found in the Capsicum annuum or Capsicum frutescens plant (aka red chiles), including Capsaicin. Aflatoxin and N-nitroso compounds (N-nitrosodimethylamine and N-nitrosopyrrolidine) have been detected as contaminants. The ultraviolet (UV) absorption spectrum for Capsicum Annuum Fruit Extract indicates a small peak at approximately 275 nm, and a gradual increase in absorbance, beginning at approximately 400 nm. Capsicum and paprika are generally recognized as safe by the U.S. Food and Drug Administration for use in food. Hexane, chloroform, and ethyl acetate extracts of Capsicum Frutescens Fruit at 200 mg/kg resulted in death of all mice. In a short-term inhalation toxicity study using rats, no difference was found between vehicle control and a 7% Capsicum Oleoresin solution. In a 4-week feeding study, red chilli (Capsicum annuum) in the diet at concentrations up to 10% was relatively nontoxic in groups of male mice. In an 8-week feeding study using rats, intestinal exfoliation, cytoplasmic fatty vacuolation and centrilobular necrosis of hepatocytes, and aggregation of lymphocytes in the portal areas were seen at 10% Capsicum Frutescens Fruit, but not 2%. Rats fed 0.5 g/kg day-1 crude Capsicum Fruit Extract for 60 days exhibited no significant gross pathology at necropsy, but slight hyperemia of the liver and reddening of the gastric mucosa were observed. Weanling rats fed basal diets supplemented with whole red pepper at concentrations up to 5.0% for up to 8 weeks had no pathology of the large intestines, livers, and kidneys, but destruction of the taste buds and keratinization and erosion of the gastrointestinal (GI) tract were noted in groups fed 0.5% to 5.0% red pepper. The results of 9-and 12-month extension of this study showed normal large intestines and kidneys. In rabbits fed Capsicum Annuum Powder at 5 mg/kg day-1 in the diet daily for 12 months damage to the liver and spleen was noted. A rabbit skin irritation test of Capsicum Annuum Fruit Extract at concentrations ranging from 0.1% to 1.0% produced no irritation, but Capsicum Frutescens Fruit Extract induced concentration-dependent (at 25 to 500 microg/ml) cytotoxicity in a human buccal mucosa fibroblast cell line. An ethanol extract of red chili was mutagenic in Salmonella typhimurium TA98, but not in TA100, or in Escherichia coli. Other genotoxicity assays gave a similar pattern of mixed results. Adenocarcinoma of the abdomen was observed in 7/20 mice fed 100 mg red chilies per day for 12 months; no tumors were seen in control animals. Neoplastic changes in the liver and intestinal tumors were observed in rats fed red chili powder at 80 mg/kg day-1 for 30 days, intestinal and colon tumors were seen in rats fed red chili powder and 1,2-dimethyl hydrazine, but no tumors were observed in controls. In another study in rats, however, red chile pepper in the diet at the same dose decreased the number of tumors seen with 1,2-dimethylhydrazine. Other feeding studies evaluated the effect of red chili peppers on the incidence of stomach tumors produced by N-methyl-N'-nitro-N-nitrosoguanidine, finding that red pepper had a promoting effect. Capsicum Frutescens Fruit Extract promoted the carcinogenic effect of methyl(acetoxymethyl)nitrosamine (carcinogen) or benzene hexachloride (hepatocarcinogen) in inbred male and female Balb/c mice dosed orally (tongue application). Clinical findings include symptoms of cough, sneezing, and runny nose in chili factory workers. Human respiratory responses to Capsicum Oleoresin spray include burning of the throat, wheezing, dry cough, shortness of breath, gagging, gasping, inability to breathe or speak, and, rarely, cyanosis, apnea, and respiratory arrest. A trade name mixture containing 1% to 5% Capsicum Frutescens Fruit Extract induced very slight erythema in 1 of 10 volunteers patch tested for 48 h. Capsicum Frutescens Fruit Extract at 0.025% in a repeated-insult patch test using 103 subjects resulted in no clinically meaningful irritation or allergic contact dermatitis. One epidemiological study indicated that chili pepper consumption may be a strong risk factor for gastric cancer in populations with high intakes of chili pepper; however, other studies did not find this association. Capsaicin functions as an external analgesic, a fragrance ingredient, and as a skin-conditioning agent--miscellaneous in cosmetic products, but is not in current use. Capsaicin is not generally recognized as safe and effective by the U.S. Food and Drug Administration for fever blister and cold sore treatment, but is considered to be safe and effective as an external analgesic counterirritant. Ingested Capsaicin is rapidly absorbed from the stomach and small intestine in animal studies. Subcutaneous injection of Capsaicin in rats resulted in a rise in the blood concentration, reaching a maximum at 5 h; the highest tissue concentrations were in the kidney and lowest in the liver. In vitro percutaneous absorption of Capsaicin has been demonstrated in human, rat, mouse, rabbit, and pig skin. Enhancement of the skin permeation of naproxen (nonsteroidal anti-inflammatory agent) in the presence of Capsaicin has also been demonstrated. Pharmacological and physiological studies demonstrated that Capsaicin, which contains a vanillyl moiety, produces its sensory effects by activating a Ca2 +-permeable ion channel on sensory neurons. Capsaicin is a known activator of vanilloid receptor 1. Capsaicin-induced stimulation of prostaglandin biosynthesis has been shown using bull seminal vesicles and rheumatoid arthritis synoviocytes. Capsaicin inhibits protein synthesis in Vero kidney cells and human neuroblastoma SHSY-5Y cells in vitro, and inhibits growth of E. coli, Pseudomonas solanacearum, and Bacillus subtilis bacterial cultures, but not Saccharomyces cerevisiae. Oral LD50 values as low as 161.2 mg/kg (rats) and 118.8 mg/kg (mice) have been reported for Capsaicin in acute oral toxicity studies, with hemorrhage of the gastric fundus observed in some of the animals that died. Intravenous, intraperitoneal, and subcutaneous LD50 values were lower. In subchronic oral toxicity studies using mice, Capsaicin produced statistically significant differences in the growth rate and liver/body weight increases. Capsaicin is an ocular irritant in mice, rats, and rabbits. Dose-related edema was observed in animals receiving Capsaicin injections into the hindpaw (rats) or application to the ear (mice). In guinea pigs, dinitrochlorobenzene contact dermatitis was enhanced in the presence of Capsaicin, injected subcutaneously, whereas dermal application inhibited sensitization in mice. Immune system effects have been observed in neonatal rats injected subcutaneously with Capsaicin. Capsaicin produced mixed results in S. typhimurium micronucleus and sister-chromatid exchange genotoxicity assays. Positive results for Capsaicin were reported in DNA damage assays. Carcinogenic, cocarcinogenic, anticarcinogenic, antitumorigenic, tumor promotion, and anti-tumor promotion effects of Capsaicin have been reported in animal studies. Except for a significant reduction in crown-rump length in day 18 rats injected subcutaneously with Capsaicin (50 mg/kg) on gestation days 14, 16, 18, or 20, no reproductive or developmental toxicity was noted. In pregnant mice dosed subcutaneously with Capsaicin, depletion of substance P in the spinal cord and peripheral nerves of pregnant females and fetuses was noted. In clinical tests, nerve degeneration of intracutaneous nerve fibers and a decrease in pain sensation induced by heat and mechanical stimuli were evident in subjects injected intradermally with Capsaicin. An increase in mean inspiratory flow was reported for eight normal subjects who inhaled nebulized 10(-7) M Capsaicin. The results of provocative and predictive tests involving human subjects indicated that Capsaicin is a skin irritant. Overall, studies suggested that these ingredients can be irritating at low concentrations. Although the genotoxicity, carcinogenicity, and tumor promotion potential of Capsaicin have been demonstrated, so have opposite effects. Skin irritation and other tumor-promoting effects of Capsaicin appear to be mediated through interaction with the same vanilloid receptor. Given this mechanism of action and the observation that many tumor promoters are irritating to the skin, the Panel considered it likely that a potent tumor promoter may also be a moderate to severe skin irritant. Thus, a limitation on Capsaicin content that would significantly reduce its skin irritation potential is expected to, in effect, lessen any concerns relating to tumor promotion potential. Because Capsaicin enhanced the penetration of an anti-inflammatory agent through human skin, the Panel recommends that care should be exercised in using ingredients that contain Capsaicin in cosmetic products. The Panel advised industry that the total polychlorinated biphenyl (PCB)/pesticide contamination should be limited to not more than 40 ppm, with not more than 10 ppm for any specific residue, and agreed on the following limitations for other impurities: arsenic (3 mg/kg max), heavy metals (0.002% max), and lead (5 mg/kg max). Industry was also advised that aflatoxin should not be present in these ingredients (the Panel adopted < or =15 ppb as corresponding to "negative" aflatoxin content), and that ingredients derived from Capsicum annuum and Capsicum Frutescens Plant species should not be used in products where N-nitroso compounds may be formed. (ABSTRACT TRUNCATED)

Where did the Chili Get its Spice? Biogeography of Capsaicinoid Production in Ancestral Wild Chili Species

The biogeography of pungency in three species of wild chili in the chaco and surrounding highland habitats of southeastern Bolivia is described. We report that Capsicum chacoense, C. baccatum, and C. eximium are polymorphic for production of capsaicin and its analogs, such that completely pungent and completely nonpungent individuals co-occur in some populations. In C. chacoense, the density of plants and the proportion of pungent plants increased with elevation. Above 900 m, all individuals in all populations except two were pungent; nonpungent individuals in at least one of the two polymorphic populations were likely a result of spreading by humans. The occurrence of pungent and nonpungent individuals in three species of ancestral Capsicum and the geographic variation of pungency within species suggest that production of capsaicin and its analogs entails both costs and benefits, which shift from one locality to another. Determining the selection pressures behind such shifts is necessary to understand the evolution of pungency in chilies.

Determination of capsaicin and zucapsaicin in human serum by high-performance liquid chromatography with fluorescence detection

A reversed-phase high-performance liquid chromatographic (HPLC) assay was developed to analyze capsaicin and zucapsaicin (civamide) in human serum at concentrations from 1 to 100 ng/ml. Human serum specimens were extracted twice with hexane-methyl tert.-butyl ether (1:1). The chromatographic separation was carried out on a C18 column at 40 degrees C using a mobile phase consisting of 40% acetonitrile in water with 5% tetrahydrofuran and 1% acetic acid. The concentration of the eluting compounds was monitored by a fluorescence detector with excitation at 270 nm and an emission cutoff of 300 nm. No interferences were observed from the extract of blank serum. The standard curves were linear in the detection range. The relative standard deviation of the assay was better than 8.4%. The limit of detection was 0.5 ng/ml.

Enzymic oxidation of capsaicin

The oxidation of capsaicin (8-methyl-N-vanillyl-6-nonenamide) has been investigated by means of electrochemical, enzymic and chemical procedures. Capsaicin appears to form a fluorescent dimer comparable with those known to be formed from some other compounds bearing the vanillyl(4-hydroxy-3-methoxybenzyl-) group. If such a dimer of capsaicin were to be formed in tissues, it would bind tightly to lipid structures and its formation would prove difficult to follow. Tests on other substances bearing the vanillyl group that might be used to investigate the dimerization reaction in tissues and tissue extracts showed that 4-hydroxy-3-methoxyphenylacetic acid is a poor second substrate for peroxidase reactions. It was found that 2-methoxy-4-methylphenol (creosol) was more suitable. These results support the suggestion that the oxidation of capsaicin may be involved in some of its biological actions.

A spinal mechanism of action is involved in the antinociception produced by the capsaicin analogue NE 19550 (olvanil)

We have studied the effect of NE 19550 (olvanil, N-(4-hydroxy-3-methoxyphenyl) methyl-9Z-octadecenamide), a capsaicin analogue with approximately equipotent antinociceptive activity in vivo compared with capsaicin, on nociceptive responses recorded from spinal dorsal horn neurones in vivo and from a spinal ventral root in vitro. In adult rats anaesthetized with halothane, antinociceptive doses of olvanil (20-40 mumol/kg, s.c.) reduced C-fibre responses evoked in wide dynamic range, lumbar dorsal horn neurones, by peripheral transcutaneous electrical stimulation. Intradermal injection of olvanil, localized to a discrete region of the peripheral receptive field, did not activate C-fibres nor change C-fibre evoked activation of dorsal horn neurones. Spinal intrathecal administration of olvanil attenuated C-fibre evoked responses and, at the highest concentration, significantly reduced A beta-fibre evoked activity. In the neonatal rat spinal cord/tail preparation maintained in vitro, superfusion of the cord with olvanil (500 nM-5 microM) did not evoke a depolarization but responses to peripheral noxious stimulation were attenuated. In a similar in vitro preparation of the neonatal rat spinal cord, the release of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) was measured in spinal cord superfusates. Capsaicin (2-10 microM) evoked a large release of CGRP-LI but olvanil (2-10 microM) produced only a small or undetectable release. Following the administration of each substance, however, the release of CGRP-LI evoked by a depolarizing potassium stimulus was significantly attenuated. These data indicate that C-fibre input to the dorsal horn was attenuated by acute systemic doses of olvanil that were antinociceptive in behavioural tests. This effect was unlikely to be due to impairment of C-fibre function by a peripheral locus of action but was more consistent with an action in the spinal cord in which the reduced release of a neurotransmitter substance from afferent nerve terminals may play a prominent role.

Antinociception produced by capsaicin: spinal or peripheral mechanism?

We have studied the effects of capsaicin, administered at concentrations found to be antinociceptive in behavioural tests, on nociceptive responses evoked both in spinal dorsal horn neurons in vivo and in spinal ventral roots in vitro. In halothane anesthetized rats, C-fibre evoked input produced by transcutaneous electrical stimulation in the peripheral receptive field was recorded from single wide dynamic range neurons located in superficial and deep dorsal horn of the lumbar spinal cord. This input was reduced by systemic administration of capsaicin at an antinociceptive dose (20 mumol/kg s.c.). Intradermal injections of capsaicin localized to the peripheral receptive field produced a transient increase in C-fibre evoked activity followed by a prolonged period of localized insensitivity to C-fibre stimulation. Spinal i.t. administered capsaicin also produced a rapid but reversible attenuation of peripherally evoked C-fibre input. In a neonatal rat spinal cord-tail preparation maintained in vitro, superfusion of the spinal cord with capsaicin (100-500 nM) produced a transient depolarization which was followed by an attenuation of responses to peripheral noxious heat and to spinal administration of substance P. Similar activity was produced by a prolonged superfusion of the spinal cord with substance P (50-200 nM). An HPLC method was used to estimate the concentration of capsaicin in a number of tissues following s.c. administration at an antinociceptive dose. In addition capsaicin concentrations were determined in the spinal cord following an i.t. administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Capsaicin, a pungent principle of hot red pepper, evokes catecholamine secretion from the adrenal medulla of anesthetized rats

Using a direct monitoring system for catecholamine (CA) secretion into the adrenal vein, we have demonstrated that capsaicin (CAP) evokes CA secretion from the adrenal medulla of pentobarbital-anesthetized rats. A significant increase in epinephrine (E) secretion was seen in rats infused with CAP (200 micrograms/kg, i.v.) without a detectable lag after the infusion. Norepinephrine (NE) secretion evoked by CAP was fairly weak compared with E secretion. The secretion of E evoked by CAP was dose-amount dependent. The stimulation of E release by CAP was barely detectable at 20 micrograms/kg, half-maximal at 100 micrograms/kg, and maximal at 600 micrograms/kg. When CAP (200 micrograms/kg) was infused into rats, the weight-ratio of E to NE was significantly higher (47.6) than when acetylcholine (12.5 micrograms/kg) was infused (13.0). These results indicate that CAP can evoke CA secretion from the adrenal medulla of rats.