Inhibition effects of Vernonia cinerea active compounds against cytochrome P450 2A6 and human monoamine oxidases, possible targets for reduction of tobacco dependence

Traditional Uses, Phytochemistry, and Pharmacological Activities of Vernonia cinerea (L.) Less.: An Updated Review

Vernonia cinerea (L.) Less. is a perennial herbaceous plant found mainly in tropical areas, particularly in Southeast Asia, South America, and India. Various parts of V. cinerea have traditionally been used in folk medicine to treat several diseases, such as malaria, fever, and liver diseases. V. cinerea has so far yielded about 92 secondary metabolites. The majority of these are sesquiterpene lactones, but triterpenes, flavonoids, steroids, phenolics, and other compounds are present as well. V. cinerea crude extracts reportedly exhibit anti-inflammatory, antiprotozoal, antidiabetic, anticancer, antimicrobial, antioxidant, and renoprotective activities. This study aims to provide the latest up-to-date information on the botanical characterization, distribution, traditional uses, phytochemistry, and pharmacological activity of V. cinerea. Information on V. cinerea was thoroughly reviewed. The literature published between 1950 and 2024 was compiled through online bibliographic databases, including SciFinder, Web of Science, Google Scholar, PubMed, ScienceDirect, Springer Link, Wiley, and the MDPI online library. The keywords used for the literature search included Vernonia cinerea (L.) Less. and the synonyms Cyanthillium cinereum (L.) H.Rob., Conyza cinerea L., and various others.

Role of Herbal Medication in Tobacco Cessation Treatment: A Systematic Review and Meta-analysis

BACKGROUND

Literature reports randomized trials have examined herbal drugs and other smoking cessation therapies such as aromatherapy acupuncture but no comprehensive overview of the overall results has been provided. The present systematic review and meta-analysis aimed to describe the overall effectiveness and safety of herbal medicines.

METHODS

This study was conducted from December 2020 to April 2021 by searching seven databases. Herbal drugs have been shown to help people quit smoking in randomized controlled studies. Two teams of researchers independently extracted the data.

FINDINGS

A total of 12 trials with 762 smokers were included in this study. The heterogeneity I2 was 43.6% with P=0.03 (Cochrane Q test) and χ2=15.77. The overall odds ratio (OR) at 95% confidence interval (CI) was 0.91 (0.68- 1.20) which shows a protective factor of herbal preparations and very low heterogeneity. The herbal treatments such as Vernonia cinerea, St. John's Wort, and lavender essential oil were significantly related to a higher continuous abstinence rate (CAR) compared to the controls with risk ratio (RR): 2.13 (0.57-4.61) at week 8; RR: 2.72 (0.77-5.3) at week 12; and RR: 2.77 (0.37-1.13) at week 24. A 7-day point abstinence rate (PAR) at week 8 was RR: 1.24 (0.81-6.34) with 95% CI; RR: 2.09 (0.93-8.29) at week 12, and RR: 2.11 (0.3-3.08) at week 24. Black pepper and lime were better in craving reduction than the placebo group. This study found no significant difference between the treatment and control groups in adverse effects, despite some minor side effects with herbal drugs.

CONCLUSION

The results of this study showed herbal treatments have the potential to help smokers quit the habit. Further well-designed trials comparing standardized herbal medicines with conventional therapy and placebo are recommended to reinforce this data.

Development of a DNA barcode library of plants in the Thai Herbal Pharmacopoeia and Monographs for authentication of herbal products

Traditional herbal medicine has long been practiced as a method of health care in many countries worldwide. The usage of herbal products has been increasing and is expected to continue to do so in the future. However, admixture and adulteration are concerns regarding the quality of herbal medicine, including its safety and efficacy. We aimed to develop a reference DNA barcode library of plants listed in the Thai Herbal Pharmacopoeia (THP) and Monographs of Selected Thai Materia Medica (TMM) (n = 101 plant species) using four core barcode regions, namely, the ITS2, matK, rbcL and trnH-psbA intergenic spacer regions, for authentication of the plant origin of raw materials and herbal products. Checking sequences from samples obtained from local markets and the Thai Food and Drug Administration (Thai FDA) against our digital reference DNA barcode system revealed the authenticity of eighteen out of twenty tested samples as claimed on their labels. Two samples, no. 3 and 13, were not Cyanthillium cinereum (L.) H.Rob. and Pueraria candollei Wall. ex Benth. as claimed, respectively. They were recognized as Emilia sonchifolia (L.) DC. and Butea superba (Roxb.), respectively. Hence, it is important for the Thai FDA or regulatory agencies to immediately initiate strict enforcement for the development of pharmacopoeial standards as well as revisions or modifications of available regulatory guidelines and to implement close monitoring for the quality control of herbal products in terms of authentication before they enter the herbal market. The centralized digital reference DNA barcode database developed here could play a very important role in monitoring or checking the authenticity of medicinal plants.

Efficacy of Vernonia cinerea (L) Less for smoking cessation: An updated meta-analysis of randomized controlled trials

Vernonia cinerea (VC) has been used for smoking cessation. A previous meta-analysis (MA) reported the efficacy of VC in smoking cessation. However, there have been updated randomized controlled trials (RCTs) on the efficacy of VC for smoking cessation, and the previous MA lacked pooled adverse events (AEs) related to VC. The objective of this study was to systematically review and perform an updated MA on the efficacy of VC for smoking cessation continuous abstinence rate (CAR), prevalence abstinence (PAR), and AE. The research articles were retrieved via electronic databases including PubMed, Science Direct, Web of Science, Thai-Journal Citation Index Center (TCI), and ThaiLis. Ten RCTs published prior to 2019 were included in this study. The number of participants in the studies ranged from 35 to 172, and the follow-up duration for the primary outcomes was 2-12 weeks. Our updated MA found that VC could significantly improve CAR2 (RR=1.54; 95% CI = 1.06, 2.23), CAR4 (RR=1.65; 95% CI = 1.25, 2.17), CAR 8 (RR=1.85; 95% CI = 1.25, 2.75), CAR12 (RR=2.56; 95% CI = 1.66, 3.95), and CAR16 (RR=2.21; 95% CI = 1.03, 4.73). Moreover, VC improved PAR2 (RR=1.47; 95% CI = 1.06, 2.04), PAR4 (RR=1.35; 95% CI = 1.02, 1.79), PAR8 (RR=1.60; 95% CI = 1.11, 2.31), and PAR12 (RR=1.70; 95% CI = 1.25, 2.30). There was no significant difference in the AE between the two groups. The study substantiates claims that VC products are effective in assisting with smoking cessation.

Novel Perceptions on Chemical Profile and Biopharmaceutical Properties of Mentha spicata Extracts: Adding Missing Pieces to the Scientific Puzzle

Mentha spicata is one of the most popular species in the genus, and it is of great interest as a gastrointestinal and sedative agent in the folk medicine system. In this study, different M. spicata extracts, obtained by the use of four solvents (hexane, chloroform, acetone and acetone/water) were chemically characterized using HPLC-ESI-MS n, which allowed for identification of 27 phenolic compounds. The extracts' antioxidant and enzyme inhibitory properties were investigated. In addition, neuroprotective effects were evaluated in hypothalamic HypoE22 cells, and the ability of the extracts to prevent the hydrogen peroxide-induced degradation of dopamine and serotonin was observed. The best antioxidant effect was achieved for all the extraction methods using acetone/water as a solvent. These extracts were the richest in acacetin, eriodictyol, hesperidin, sagerinic acid, naringenin, luteolin, chlorogenic acid, chrysoeriol and apigenin. The intrinsic antioxidant and enzyme inhibition properties of the acetone/water extract could also explain, albeit partially, its efficacy in preventing prostaglandin E2 overproduction and dopamine depletion (82.9% turnover reduction) in HypoE22 cells exposed to hydrogen peroxide. Thus, our observations can provide a scientific confirmation of the neuromodulatory and neuroprotective effects of M. spicata.

Evaluation of Anti-Inflammatory Effect of Moringa oleifera Lam. and Cyanthillium cinereum (Less) H. Rob. Lozenges in Volunteer Smokers

Smokers have high plaque accumulation that initiates gingival inflammation and progresses to periodontitis. Thus, oral hygiene to control microbial plaque formation is an effective method of preventing gingivitis. Medicinal plants such as Moringa oleifera Lam. (MO) and Cyanthillium cinereum (Less.) H. Rob. (CC) have an anti-inflammatory effect that might improve oral health in smokers. This study evaluated the effect of MO leaf and CC extracts using MO lozenges and a combination of MO + CC lozenges on oral inflammation and gingivitis in volunteer smokers. Lozenges consisting of MO and CC extracts were developed and studied in vivo. The results showed that lozenges significantly reduced oral inflammation and gingivitis in volunteers. The gingival index (GI) of group III (MO + CC lozenges) significantly decreased, while the percentage decrease of oral inflammation in group II (MO lozenges) was significantly higher than the other groups. The percentage decrease of GI values in group II (MO lozenges) and group III (MO + CC lozenges) were significantly higher than the placebo group I. Our findings indicated that MO and MO + CC lozenges reduced oral inflammation and gingivitis and showed potential to improve oral health in smokers.

Identification of CYP 2A6 inhibitors in an effort to mitigate the harmful effects of the phytochemical nicotine

AIM

In this study, our goal was to study the inhibition of nicotine metabolism by P450 2A6, as a means for reduction in tobacco use and consequently the prevention of smoking-related cancers. Nicotine, a phytochemical, is an addictive stimulant, responsible for the tobacco-dependence in smokers. Many of the other phytochemicals in tobacco, including polycyclic aromatic hydrocarbons, N-nitrosamines, and aromatic amines, are potent systemic carcinogens. Tobacco smoking causes about one of every five deaths in the United States annually. Nicotine plasma concentration is maintained by the smokers' smoking behavior within a small range. Nicotine is metabolized by cytochrome P450s 2A6 and 2A13 to cotinine. This metabolism causes a decrease in nicotine plasma levels, which in turn leads to increased tobacco smoking, and increased exposure to the tobacco carcinogens.

METHODS

Using the phytochemical nicotine as a lead structure, and taking its interactions with the P450 2A6 binding pocket into consideration, new pyridine derivatives were designed and synthesized as potential selective mechanism-based inhibitors for this enzyme.

RESULTS

The design and synthesis of two series of novel pyridine-based compounds, with varying substituents and substitution locations on the pyridine ring, as well as their inhibitory activities on cytochrome P450 2A6 and their interactions with its active site are discussed here. Substitutions at position 3 of the pyridine ring with an imidazole or propargyl ether containing group showed the most optimal interactions with the P4502A6 active site.

CONCLUSION

The pyridine compounds with an imidazole or propargyl ether containing substituent on position 3 were found to be promising lead compounds for further development. Hydrogen-bonding interactions were determined to be crucial for effective binding of these molecules within the P450 2A6 active site.

Mechanism-based inactivation of cytochrome P450 enzymes by natural products based on metabolic activation

Cytochrome P450 enzymes (P450 enzymes) are the most common and important phase I metabolic enzymes and are responsible for the majority of the metabolism of clinical drugs and other xenobiotics. Drug-drug interactions (DDIs) can occur when the activities of P450 enzymes are inhibited. In particular, irreversible inhibition of P450 enzymes may lead to severe adverse interactions, compared to reversible inhibition. Many natural products have been shown to be irreversible inhibitors of P450 enzymes. The risks for intake of naturally occurring irreversible P450 enzyme inhibitors have been rising due to the rapid growth of the global consumption of natural products. Irreversible inhibition is usually called mechanism-based inactivation, which is time-, concentration- and NADPH- dependent. Generally, the formation of electrophilic intermediates is fundamental for the inactivation of P450 enzymes. This review comprehensively classifies natural P450 enzyme inactivators, including terpenoids, phenylpropanoids, flavonoids, alkaloids, and quinones obtained from herbs or foods. Moreover, the structure - activity correlations according to the IC₅₀ (or K_i) values reported in the literature as well as the underlying mechanisms based on metabolic activation are highlighted in depth.

Differentiation of Cyanthillium cinereum, a smoking cessation herb, from its adulterant Emilia sonchifolia using macroscopic and microscopic examination, HPTLC profiles and DNA barcodes

Cyanthillium cinereum (L.) H.Rob. is one of the most popular herbal smoking cessation aids currently used in Thailand, and its adulteration with Emilia sonchifolia (L.) DC. is often found in the herbal market. Therefore, the quality of the raw material must be considered. This work aimed to integrate macro- and microscopic, chemical and genetic authentication strategies to differentiate C. cinereum raw material from its adulterant. Different morphological features between C. cinereum and E. sonchifolia were simply recognized at the leaf base. For microscopic characteristics, trichome and pappus features were different between the two plants. HPTLC profiles showed a distinct band that could be used to unambiguously differentiate C. cinereum from E. sonchifolia. Four triterpenoid compounds, β-amyrin, taraxasterol, lupeol, and betulin, were identified from the distinct HPTLC band of C. cinereum. The use of core DNA barcode regions; rbcL, matK, ITS and psbA-trnH provided species-level resolution to differentiate the two plants. Taken together, the integration of macroscopic and microscopic characterization, phytochemical analysis by HPTLC and DNA barcoding distinguished C. cinereum from E. sonchifolia. The signatures of C. cinereum obtained here can help manufacturers to increase the quality control of C. cinereum raw material in commercialized smoking cessation products.

Structure-activity relationship and in vitro inhibition of human cytochrome CYP2A6 and CYP2A13 by flavonoids

Cigarette smoking is one of the major risk factors of various diseases including respiratory diseases and lung cancer. While the liver-specific CYP2A6 is associated with the nicotine clearance and smoking addiction, the metabolic activation of the tobacco-specific nitrosamine by lung-specific CYP2A13 can lead to lung tumorigenesis.It has been reported that inhibition of CYP2A6 and CYP2A13 enzymes by flavonoids constituents could be an aids in smoking cessation. This study demonstrates the inhibition activity of kaempferol and myricetin and the structure-function relationship of these two flavonoids and previously isolated flavonoids from Vernonia cinerea and Pluchea indica against both enzymes.Kaempferol could inhibit CYP2A6 with K_ic value of 1.77 ± 0.47 µM while inhibit CYP2A13 with K_ic value of 0.12 ± 0.01 µM. Myricetin could inhibit CYP2A6 with K_ic value of 4.06 ± 0.52 µM while inhibit CYP2A13 with K_ic value of 1.88 ± 0.03 µM.Molecular docking indicated that CYP2A13 enzyme has strong hydrophobic interaction with ring B of flavonoids compared to CYP2A6 enzyme. The presence of the hydroxyl group at C3 position of ring C and the hydroxyl group at C5' of ring B affected inhibitory activity on both enzymes.

Anti-proliferative effect of 8α-tigloyloxyhirsutinolide-13-O-acetate (8αTGH) isolated from Vernonia cinerea on oral squamous cell carcinoma through inhibition of STAT3 and STAT2 phosphorylation

BACKGROUND

The high mortality rate of oral cancers has stimulated the search for effective herbal medicines and their pharmacological targets. Vernonia cinerea, a perennial tropical herb, is wildly used as a traditional folk medicine for treatment of intestinal diseases and various skin diseases in addition to possessing anti-cancer activity. However, the effect of 8α-tigloyloxyhirsutinolide-13-O-acetate (8αTGH) as a major sesquiterpene lactone compound found in V. cinerea and the underlying mechanism of its action on oral cancer cells remains unknown.

PURPOSE

To investigate the anti-cancer activity of 8αTGH extracted from V. cinerea and the underlying mechanism of its action in oral cancer cells.

METHODS

The anti-proliferative effect of 8αTGH on oral squamous cell carcinoma (HSC4) and lung carcinoma (A549) was determined using the SRB colorimetric method. The molecular mechanism of 8αTGH was explored using kinase inhibitors, followed by Western blotting or RT-qPCR. Flow cytometry and Western blotting were used to assess cell cycle arrest.

RESULTS

8αTGH inhibited cancer cell growth more effectively on HSC4 than A549 and was much less effective on tested normal oral cells. 8αTGH inhibited STAT3 phosphorylation on both cancer cells. Notably, 8αTGH was able to suppress the constantly activated STAT2 found only in HSC4. The STAT2 inhibition by 8αTGH consequently caused down-regulation of ISG15 and ISG15 conjugates. As a result, decreased expression of CDK1/2 and Cyclin B1 was detected leading to G2/M cell cycle arrest.

CONCLUSION

8αTGH isolated from V. cinerea preferentially inhibits the proliferation of oral cancer cells by causing G2/M cell cycle arrest via inhibition of both STAT3 and STAT2 phosphorylation. The results provide molecular bases for developing 8αTGH as a drug candidate or a complementary treatment of oral cancer.

Dietary effects of Sideritis scardica "mountain tea" on human in vivo activities of xenobiotic metabolizing enzymes in healthy subjects

Sideritis scardica(S. scardica) is an endemic plant of the Balkan Peninsula traditionally used as herbal tea for inflammation and gastric disorders. Aqueous herbal extracts may affect the activity of Phase I and II enzymes involved in xenobiotic metabolism. The purpose of the present study was to determine whether S. scardica decoction alters the activity of CYP1A2, CYP2A6, XO, NAT2 and UGT1A1/1A6 enzymes in humans. Fourteen healthy subjects consumed S. scardica decoction for six days. Enzyme phenotyping was assessed in saliva and urine using caffeine and paracetamol metabolite ratios as follows: CYP1A2: 17X/137X (saliva) and (AFMU+1U+1X)/17U, CYP2A6: 17U/(17U + 17X), XO: 1U/(1U+1X), NAT2: AFMU/(AFMU+1U+1X) and UGT1A1/1A6: glucuronidated/total paracetamol (urine). After S. scardica intake, CYP1A2 index was reduced by ∼16% and ∼8% in saliva (before: 0.54 ± 0.18, after: 0.46 ± 0.09; p = 0.08) and urine (before: 3.59 ± 0.52, after: 3.67 ± 0.78; p = 0.12), respectively. CYP2A6 index was significantly reduced only in males (before: 0.76 ± 0.08, after: 0.67 ± 0.07; p = 0.004), suggesting sexual dimorphism in CYP2A6 inhibition. There was no effect of Sideritis scardica treatment on XO, NAT2 or UGT1A1/1A6 indices. Usual consumption of the aerial parts of S. scardica decoction is unlikely to result in herb-drug interactions involving the enzymes studied, with the exception of potential herb-CYP2A6 substrate interaction in males.

Efficacy and safety of Vernonia cinerea (L.) Less. for smoking cessation: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND & OBJECTIVE

Several randomized controlled trials have investigated Vernonia cinerea (L.) Less. for smoking cessation but there remains no critical summary of overall findings. This study uses systematic review and meta-analysis to summarize the efficacy and safety of V. cinerea.

METHODS

Nine databases were searched through November 2017. Randomized controlled trials that reported the smoking cessation effect of V. cinerea were included. Data were extracted by two independent researchers. Study quality was assessed using the Cochrane risk of bias and JADAD score. The estimates of pooled effects were calculated as relative risk (RR) with 95% CI using a random-effects model.

RESULTS

Five trials with 347 smokers were included. V. cinerea treatment group was significantly associated with cessation rate higher than that in the control group with no evidence of heterogeneity for both continuous abstinence rate (CAR) at week 8 with risk ratio (RR): 1.69, 95% CI [1.00, 2.86]; week 12 RR: 2.18, 95% CI [1.17, 4.04]) and 7-day point prevalence abstinence rate (PAR) (week 8 RR: 1.51, 95% CI [1.01, 2.27]; week 12 RR: 1.93, 95% CI [1.24, 2.99]) at week 8 and 12, respectively. There was no significant difference of all adverse events between the treatment and the control groups.

CONCLUSION

Our study demonstrates that V. cinerea has potential efficacy for smoking cessation. Further well-design RCTs of standardized V. cinerea compared with standard treatment should be conducted to strengthen this evidence.

Effects of Vernonia cinerea Compounds on Drug-metabolizing Cytochrome P450s in Human Liver Microsomes

Vernonia cinerea has been widely used in traditional medicines for various diseases and shown to aid in smoking abstinence and has anticancer properties. V. cinerea bioactive compounds, including flavonoids and hirsutinolide-type sesquiterpene lactones, have shown an inhibition effect on the nicotine-metabolizing cytochrome P450 2A6 (CYP2A6) enzyme and hirsutinolides reported suppressing cancer growth. In this study, V. cinerea ethanol extract and its bioactive compounds, including four flavonoids and four hirsutinolides, were investigated for an inhibitory effect on human liver microsomal CYPs 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4 using cocktail inhibition assays combined with LC-MS/MS analysis. Among tested flavonoids, chrysoeriol was more potent in inhibition on CYP2A6 and CYP1A2 than other liver CYPs, with better binding efficiency toward CYP2A6 than CYP1A2 (K_i values in competitive mode of 1.93 ± 0.05 versus 3.39 ± 0.21 μM, respectively). Hirsutinolides were prominent inhibitors of CYP2A6 and CYP2D6, with IC₅₀ values of 12-23 and 15-41 μM, respectively. These hirsutinolides demonstrated time-dependent inhibition, an indication of mechanism-based inactivation, toward CYP2A6. Quantitative prediction of microsomal metabolism of these flavonoids and hirsutinolides, including half-lives and hepatic clearance rate, was examined. These findings may have implications for further in vivo studies of V. cinerea. Copyright © 2017 John Wiley & Sons, Ltd.

Inhibition of human cytochromes P450 2A6 and 2A13 by flavonoids, acetylenic thiophenes and sesquiterpene lactones from Pluchea indica and Vernonia cinerea

The human liver cytochrome P450 (CYP) 2A6 and the respiratory CYP2A13 enzymes play role in nicotine metabolism and activation of tobacco-specific nitrosamine carcinogens. Inhibition of both enzymes could offer a strategy for smoking abstinence and decreased risks of respiratory diseases and lung cancer. In this study, activity-guided isolation identified four flavonoids 1–4 (apigenin, luteolin, chrysoeriol, quercetin) from Vernonia cinerea and Pluchea indica, four hirsutinolide-type sesquiterpene lactones 5–8 from V. cinerea, and acetylenic thiophenes 9–11 from P. indica that inhibited CYP2A6- and CYP2A13-mediated coumarin 7-hydroxylation. Flavonoids were most effective in inhibition against CYP2A6 and CYP2A13, followed by thiophenes, and hirsutinolides. Hirsutinolides and thiophenes exhibited mechanism-based inhibition and in irreversible mode against both enzymes. The inactivation kinetic K_I values of hirsutinolides against CYP2A6 and CYP2A13 were 5.32–15.4 and 0.92–8.67 µM, respectively, while those of thiophenes were 0.11–1.01 and 0.67–0.97 µM, respectively.

Effects of Vernonia cinerea on reproductive performance in streptozotocin-induced diabetic rats

The present study investigated the effects of Vernonia cinerea (VC) on the reproductive function in streptozotocin (STZ)-induced diabetic male rats. Six-week-old male Sprague-Dawley rats were randomly divided into four groups: group 1, normal control rats; group 2, diabetic untreated rats; group 3, diabetic rats treated with VC (10 mg/kg); and group 4, diabetic rats treated with VC (40 mg/kg). Diabetes mellitus (DM) was induced by intraperitoneal injection of STZ (60 mg/kg). All animals were treated for 30 consecutive days. Body weight, blood glucose, food intake, epididymal sperm parameters, testicular microstructure and serum testosterone levels were evaluated. VC treatment significantly restored the sperm motility and testosterone concentration, and decreased the testicular histopathological changes in DM rats. Moreover, high-dose VC exhibited an antidibetic activity and significantly improved the sperm count. In conclusion, we found, for the first time, that administration of VC significantly restored the testicular function and testosterone concentration in diabetic male rats.