Antihyperuricemic lignans from the leaves of Phyllanthus niruri

Pharmacological activities and mechanisms of action of hypophyllanthin: A review

Hypophyllanthin is a major lignan present in various Phyllanthus species and has been used as one of the bioactive chemical markers for quality control purposes as it contributes to their diverse pharmacological activities. The objective of this study is to compile up-to-date data on the pharmacological actions and mechanisms of hypophyllanthin. This review also includes the extracts of Phyllanthus species whose pharmacological actions have been partially attributed to hypophyllanthin. The scientific findings on the compound are critically analyzed and its potential as a lead molecule for the discovery of drug candidates for the development of therapeutics to treat diverse diseases is highlighted. Data collection was mainly through the exploration of Ovid-MEDLINE, Scopus, Science Direct, and Elsevier databases. Studies conducted in vitro and in vivo showed that hypophyllanthin had potent immunomodulating properties as well as a variety of other pharmacological properties, including anti-inflammatory, hepatoprotective, anti-tumor, anti-allergic, anti-hypertensive, and phytoestrogenic properties. Several mechanisms of action on the effects of hypophyllanthin on the immune system, in cancer and other disease states, were presented to provide some insights into its pharmacological effects. Before being submitted to clinical investigations, additional animal studies utilising different animal models are necessary to analyse its bioavailability, pharmacokinetics, and pharmacodynamic properties, as well as its toxicity, to determine its efficacy and safety. Understanding its potential as a lead molecule for the discovery of therapeutic candidates, particularly for the development of therapies for inflammatory and immune-related disorders, requires an understanding of its pharmacological activities and mechanisms of action. An insight into its pharmacological activities and mechanisms of action will provide an understanding of its potential as a lead compound for the discovery of drug candidates, especially for the development of therapies for inflammatory and immune related diseases.

An insight into the potent medicinal plant Phyllanthus amarus Schum. and Thonn

Phyllanthus amarus Schum. and Thonn., a globally distributed herb is known for its several therapeutic potentials. P. amarus has a long history of use in the traditional system of medicine for over 2000 years owing to its wide array of secondary metabolites that confer significant medicinal attributes. Research on various aspects including ethnobotany, phytochemistry to bioactivity, or pharmacological studies has been conducted over the past several decades on this potent herb. P. amarus extracts have shown a broad range of pharmacological activities like hepatoprotective, antioxidant, antiviral, antimicrobial, antidiabetic, anti-inflammatory, anticancer, antimalarial, nephroprotective, diuretic, and several other properties. The present review compiles and covers literature and research of several groups across past decades to date and focuses on how the therapeutic significance of this plant can be further explored for future research either as herbal formulations, alternative medicine, or in the pharmaceutical industry.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13237-022-00409-z.

Therapeutic potential of medicinal plants for the management of renal stones: A review

Kidney stone disease is the third most common urological ailment worldwide, people. The mechanism of stone formation includes: urine supersaturation, aggregation, retention, nucleation, and growth of crystals in the cells of the renal tubular epithelium. Kidney stones may cause extreme pain and blockage of urine flow. They are usually treated with conventional drugs and shock wave (ESWL) as well as a variety of medications that may cause several adverse effects. The remaining stone fragments and the risk of infection following ESWL are major challenges in the treatment of kidney stones. Recently, despite the emergence of modern drugs, medicinal plants have been recognized and utilized in many nations clinically due to their safety profile, efficiency, cultural acceptance, and fewer side effects than approved drugs. Medicinal plants are used in different cultures as a reliable source of natural remedies. The aim of this review is to provide comprehensive information about traditionally used plants as well as their scientifically proven pharmacological activities, their primary chemical ingredients, and potential mechanisms of action, such as analgesic, astringent, demulcent, diuretic activity, antioxidant activity, inhibition of the inflammatory process, nucleation inhibition, crystallization inhibition, inhibition of crystal aggregation, reducing , reducing stone size, and reducing urine supersaturation.

Blood pressure lowering effect and vascular activity of Phyllanthus niruri extract: The role of NO/cGMP signaling pathway and β-adrenoceptor mediated relaxation of isolated aortic rings

ETHNOPHARMACOLOGICAL RELEVANCE

Phyllanthus niruri have a long history of use in the traditional treatment of various ailments including hypertension. Literature reports have indicated that it is a potent antihypertensive herbal medication used traditionally.

AIM OF THE STUDY

This study was carried out to investigate the antihypertensive and vasodilatory activity of four solvents extracts of P. niruri namely; petroleum ether (PEPN), chloroform (CLPN), methanol (MEPN) and water (WEPN), with the aim of elucidating the mechanism of action and identifying the phytochemical constituents.

MATERIALS AND METHODS

Male Spontaneous Hypertensive Rats (SHRs) were given oral gavage of P. niruri extract daily for two weeks and the blood pressure was recorded in vivo. We also determine the vasodilation effect of the extracts on rings of isolated thoracic aorta pre-contracted with phenylephrine (PE, 1 μM). Endothelium-intact or endothelium-denuded aorta rings were pre-incubated with various antagonists like 1H-[1,2,4] oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ, 10 μM) and Methylene blue (MB 10 μM), sGC inhibitors; Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME, 10 μM) a nitric oxide synthase (NOS) inhibitor; atropine (10 μM), a cholinergic receptor blocker; indomethacin (10 μM), a cyclooxygenase inhibitor and various K⁺ channel blockers such as glibenclamide (10 μM) and tetraethyl ammonium (TEA 10 μM) for mechanism study.

RESULTS

SHRs receiving P. niruri extracts showed a significant decrease in their blood pressure (BP) when compared to the baseline value, with PEPN being more potent. The extracts (0.125-4 mg/mL) also induced vasorelaxation on endothelium-intact aorta rings. PEPN elicited the most potent maximum relaxation effect (R_max). Mechanism assessment of PEPN showed that its relaxation effect is significantly suppressed in endothelium-denuded aorta rings. Pre-incubation of aorta rings with atropine, L-NAME, ODQ, indomethacin, and propranolol also significantly attenuated its relaxation effect. Conversely, incubation with TEA and glibenclamide did not show a significant effect on PEPN-induced relaxation.

CONCLUSION

This study indicates that the antihypertensive activity of P. niruri extract is mediated by vasoactive phytoconstituents that dilate the arterial wall via endothelium-dependent pathways and β-adrenoceptor activity which, in turn, cause vasorelaxation and reduce blood pressure.

Phyllanthus niruri leaves aqueous extract improves kidney functions, ameliorates kidney oxidative stress, inflammation, fibrosis and apoptosis and enhances kidney cell proliferation in adult male rats with diabetes mellitus

ETHNOPHARMACOLOGICAL RELEVANCE

Phylanthus niruri has been used to treat ailments related to the urogenital organs. In this study, this herb was hypothesized to help to ameliorate kidney disease in diabetes mellitus (DM).

AIMS

To investigate P. niruri leaves aqueous extract (PN) effects on kidney functions, histopathological changes and levels of oxidative stress, inflammation, fibrosis, apoptosis and proliferation in DM.

METHODS

PN was orally administered to streptozotocin-nicotinamide-induced male diabetic rats for 28 days. At the end of the treatment, fasting blood glucose (FBG) and kidney functions were measured. Kidney somatic index, histopathological changes and levels of RAGE, Nrf2, oxidative stress markers (TBARS, SOD, CAT and GPx), inflammatory markers (NFkβ-p65, Ikk-β, TNF-α, IL-1β and IL-6), apoptosis markers (caspase-3, caspase-9 and Bax), fibrosis markers (TGF-β1, VEGF and FGF-1) and proliferative markers (PCNA and Ki-67) were determined by biochemical assays, qPCR, Western blotting, immunohistochemistry or immunofluorescence.

RESULTS

Administration of PN helps to maintain near normal FBG, creatinine clearance (CCr), blood urea nitrogen (BUN), BUN/Cr ratio, serum electrolytes, uric acid and urine protein levels in DM. Decreased RAGE, TBARS and increased Nrf2, SOD-1, CAT and GPx-1 were observed in PN-treated diabetic rat kidneys. Expression of inflammatory, fibrosis and apoptosis markers in the kidney reduced but expression of proliferative markers increased following PN treatment. Lesser histopathological changes were observed in the kidney of PN-treated diabetic rats.

CONCLUSION

PN helps to preserve near normal kidney function and prevents histopathological changes via ameliorating oxidative stress, inflammation, fibrosis and apoptosis while enhancing proliferation of the kidney in DM.

Phytochemistry and Pharmacology of Phyllanthus niruri L.: A Review

Phyllanthus niruri, a typical member of family Euphorbiaceae, is a small annual herb found throughout the tropical and subtropical regions of both hemispheres. The genus Phyllanthus has been used in traditional medicine for its wide range of pharmacological activities like antimicrobial, antioxidant, anticancer, antiinflammatory, antiplasmodial, antiviral, diuretic and hepatoprotective. This review summarizes the information about morphological, biochemical, ethanobotanical, pharmacological, biological and toxicological activities with special emphasis on mechanism of anticancer activity of P. niruri. Gaps in previous studies such as taxonomic inconsistency of P. niruri, novel phytochemicals and their therapeutic properties, especially mechanisms of anticancerous activity and market products available, have been looked into and addressed. Scientific information related to 83 phytochemicals (including many novel compounds detected recently by the authors) has been provided in a very comprehensive manner. Copyright © 2017 John Wiley & Sons, Ltd.

The pharmacological potential of Phyllanthus niruri

INTRODUCTION

Phyllanthus niruri is a traditional shrub of the genus Phyllanthaceae with long-standing Ayurvedic, Chinese and Malay ethnomedical records. Preliminary studies from cell and animal model have provided valuable scientific evidence for its use.

AIM

This review aims to summarize selected scientific evidence on the pharmacological properties of P. niruri over the past 35 years while identifying potential areas of further development of this herb as an economical adjunct.

METHODS

The review covers literature pertaining to the evidence base therapeutic potential of P. niruri spanning from 1980 to 2015 available on PubMed.

RESULTS

Evidence suggests that the extracts of P. niruri possess hepatoprotective, antiviral, antibacterial, hypolipidaemic, hypoglycaemic, analgesic, anti-inflammatory, cardioprotective, anti-urolithiatic and antihyperuricaemic properties due its novel bioactive compounds.

CONCLUSION

Scientific evidence suggests that there is strong pharmacological potential in developing P. niruri as a drug to be used in liver disorders and in antiviral therapy. Despites this, large-scale heterogeneity in study protocol and unstandardized reporting standards limit the ability for valuable comparison and may mask the ability to replicate these studies. Thus interpretation of findings should be performed with caution and further studies should be performed in line with best practices. More cheminformatics, toxicological and mechanistic studies would aid the progress to clinical trial studies.

The Genus Phyllanthus: An Ethnopharmacological, Phytochemical, and Pharmacological Review

The plants of the genus Phyllanthus (Euphorbiaceae) have been used as traditional medicinal materials for a long time in China, India, Brazil, and the Southeast Asian countries. They can be used for the treatment of digestive disease, jaundice, and renal calculus. This review discusses the ethnopharmacological, phytochemical, and pharmacological studies of Phyllanthus over the past few decades. More than 510 compounds have been isolated, the majority of which are lignins, triterpenoids, flavonoids, and tannins. The researches of their remarkable antiviral, antioxidant, antidiabetic, and anticancer activities have become hot topics. More pharmacological screenings and phytochemical investigations are required to support the traditional uses and develop leading compounds.

Ethnobotanical study of medicinal plants by population of Valley of Juruena Region, Legal Amazon, Mato Grosso, Brazil

ETHNOPHARMACOLOGICAL IMPORTANCE

The use of medicinal plants for treatment, cure and prevention of diseases has been described by many people since time immemorial. Because of this use, commercial and scientific interests have emerged, making it necessary to realize ethnobotanical surveys of medicinal plants species, which is important for subsequent chemical and pharmacological bioprospections.

AIM OF THE STUDY

This study aimed at surveying, identifying, cataloging and documenting the medicinal plants species used in the Valley of Juruena, Northwestern Mato Grosso, Legal Amazon Brazil for the treatment of various human diseases, as well as assessed the species of interest for bioprospecting potential.

MATERIALS AND METHODS

Informants were interviewed using semi-structured form to capture information on socio-demographic and ethnopharmacological data of medicinal plants such as vernacular name, uses, geographic origin, habit, form of preparation and part used. Results were analyzed using descriptive and quantitative means: indices of use-report (Ur) and informant consensus factor (ICF), for the selection of plant species with therapeutic potential.

RESULTS

Three hundred and thirty two (332) plants species belonging to 90 families were reported for medicinal purposes and totaling 3973 use-reports were reported by 365 (92.9%) of the people interviewed. Asteraceae (32.2%), Fabaceae (26.7%) and Lamiaceae (24.4%) families were the most represented, with majority being species native (64.45%) to Brazil. Leaves (64.5%) were the part of the plant most used and infusion (45.7%) was the most utilized form. Gastrointestinal disorders followed by respiratory complaints topped the list of use-reports. The native or naturalized plants with the highest use reports in the order of decreasing absolute frequency per each emic-category are Cymbopogon citratus (DC.) Stapfc (104), Mentha pulegium L. (94), Arrabidaea chica (Humb. & Bonpl.) B. Verl. (97), Alternanthera brasiliana (L.) Kuntze (71), Baccharis crispa Spreng (57), Phyllanthus niruri L. (48), Gossypium barbadense L. (44), Solidago microglossa DC. (40) and Bauhinia forficata L. (20). And the most cited exotics are: Chenopodium ambrosioides L. (151), Aloe vera (L.) Burm. f., (89) and Rosmarinus officinalis L. (72). In some cases, high ICF values were found, which reflects high degree of homogeneity of consensus among informants in this region on medicinal plants.

CONCLUSION

The population of Valle of Juruena makes use of a wide array of medicinal plants distributed in all use categories with predominance of those use in the treatments of gastrointestinal and respiratory ailments. The therapeutic potential of some of the species of medicinal importance extensively utilized by the population of the region have been scientifically validated, and are therefore promising prototype of new drugs. However, there are some of these species whose ethnomedicinal uses are yet to be scientifically verified and thus constitute an unexplored terrain for future biological/pharmacological studies.

In vitro Xanthine Oxidase Inhibitory Studies of Lippia nodiflora and Isolated Flavonoids and Phenylethanoid Glycosides as Potential Uric Acid-lowering Agents

Lippia nodiflora has been traditionally used for treatment of knee joint pain. Hitherto, no studies have been reported on the effective use of L. nodiflora against hyperuricemia, gout or other metabolic disorders. In this present study, L. nodiflora was examined for its ability to lower uric acid levels using an in vitro xanthine oxidase inhibitory assay. The whole plant methanolic extract was subjected to bioactivity-guided fractionation to yield 4 fractions (F1–F4). F3 displayed the highest potency and was further purified by column chromatography to afford two phenylethanoid glycosides, arenarioside (1) and verbascoside (2), and three flavonoids, 6-hydroxyluteolin (3), 6-hydroxyluteolin-7- O-glycoside (4), and nodifloretin (5). These compounds inhibited xanthine oxidase activity, with IC50 values between 7.52 ± 0.01 and 130.00 ± 2.25 μM, of which 3 was the most potent. In contrast, allopurinol, serving as a positive control, was 0.22 ± 0.00 μM. Thus, L. nodiflora, and its chemical constituents are worthy of further studies as potential anti-hyperuricemic agents.

Effects of chicory inulin on serum metabolites of uric acid, lipids, glucose, and abdominal fat deposition in quails induced by purine-rich diets

Inulin, a group of dietary fibers, is reported to improve the metabolic disorders. In the present study, we investigated the effects of chicory inulin on serum metabolites of uric acid (UA), lipids, glucose, and abdominal fat deposition in quail model induced by a purine-rich diet. In this study, 60 male French quails were randomly allocated to five groups: CON (control group), MOD (model group), BEN (benzbromarone-treated group), CHI-H (high-dosage chicory inulin-treated group), and CHI-L (low-dosage chicory inulin-treated group). The serum UA level was significantly increased in the model group from days 7 to 28, as well as triglyceride (TG) and free fatty acid (FFA) increased later in the experimental period. The abdominal fat ratio was increased on day 28. Benzbromarone can decrease UA levels on days 14 and 28. The high and low dosage of chicory inulin also decreased serum UA levels on days 7, 14, and 28. The abdominal fat ratio, activity, and protein of acetyl-CoA carboxylase (ACC) were decreased in chicory inulin-treated groups. The activities of xanthine oxidase (XOD) and fatty acid synthase (FAS) were increased in the model group and decreased in the benzbromarone and chicory inulin groups. This study evaluated a quail model of induced hyperuricemia with other metabolic disorders caused by a high-purine diet. The results indicated that a purine-rich diet might contribute to the development of hyperuricemia, hypertriglyceridemia, and abdominal obesity. Chicory inulin decreased serum UA, TG, and abdominal fat deposition in a quail model of hyperuricemia by altering the ACC protein expression and FAS and XOD activities.

Isocorilagin, a Cholinesterase Inhibitor from Phyllanthus niruri

Drugs that have dual inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) produce better clinical efficacy against Alzheimer's disease (AD) than those that selectively inhibit one enzyme. A dual cholinesterase inhibitory-guided fractionation of Phyllanthus niruri leaves afforded isocorilagin, a bioactive tannin possessing good inhibitory activities against AChE (IC50: 0.49 μM) and BChE (IC50: 4.20 μM). Interestingly, isocorilagin was relatively 2- to 3-fold more potent than galanthamine, the clinically used inhibitor. The kinetic analyses suggested that isocorilagin was a non-competitive inhibitor for AChE and an uncompetitive inhibitor for BChE, with calculated Ki values of 1.49 μM and 2.86 μM, respectively. In silico molecular docking revealed that isocorilagin effectively blocked the substrate entry by forming hydrogen bonding with residues at the entrance of the AChE active site. With BChE, the compound completely docked inside and occupied the active site of the enzyme. This study demonstrated for the first time the potent cholinesterase inhibitory activities of isocorilagin, a promising lead that is worthy of further investigation.

Physicochemical characterization of phyllanthin from Phyllanthus amarus Schum. et Thonn

Phyllanthin is a major bioactive lignan component of Phyllanthus amarus, with several known biological activities. This study dealt with the isolation and physicochemical characterization of phyllanthin. Phyllanthin was isolated from P. amarus leaves by column chromatography and purified by recrystallization to obtain phyllanthin crystals with a purity of more than 98%. UV, IR, MS, (1)H NMR and (13)C NMR spectra were employed to identify phyllanthin. The physicochemical properties of phyllanthin were characterized using differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction, pH-solubility, ionization property and lipophilicity. The results indicated that phyllanthin crystals had the melting point and melting enthalpy range of 96.67-97.03 °C and 109.61-116.34 J/g, respectively. Three kinds of phyllanthin crystals, recrystallized by petroleum ether, absolute ethanol and 25% ethanol solution, showed only one polymorph and no polymorphic impurity. Phyllanthin in a solid state was found to undergo significant thermal decomposition above 200 °C. The compound demonstrated good stability in aqueous solution over a pH range of 1.07-10.02 for at least 4 h. The solubility of phyllanthin appeared to be pH-independent of pH range from 1.07 to 10.26. Ionization property studied by absorbance spectroscopy method was in agreement with the result of pH-solubility study, showing that phyllanthin has no pKa over a pH range of 1.12-10.02. The log Pow value of phyllanthin was found to be 3.30 ± 0.05 at pH 7.48, suggesting that phyllanthin may have good permeability through biological membranes. The findings could be useful tools for the development of stable and bioavailable oral dosage forms of phyllanthin.

Phyllanthin and hypophyllanthin inhibit function of P-gp but not MRP2 in Caco-2 cells

OBJECTIVES

The purposes of this study were to investigate the inhibitory effects of two lignans, phyllanthin and hypophyllanthin, on the function of P-glycoprotein (P-gp) and multidrug resistance protein 2 (MRP2), using the in-vitro model of Caco-2 cells. In addition, the effect of prolonged exposure to these two compounds on the expression of active P-gp was also determined.

METHODS

The activity of P-gp and MRP2 was determined in the uptake assays by monitoring the intracellular accumulation of their specific substrates (calcein acetoxymethyl ester and 5(6)-carboxy-2',7'-dichlorofluorescein diacetate, respectively) with fluorescence spectroscopy.

KEY FINDINGS

Hypophyllanthin and phyllanthin inhibited P-gp function with comparable potencies, but neither compound affected MRP2 activity. When the lignans were washed out before addition of substrate, the inhibitory action of both compounds against P-gp function was lost. These results suggested the reversibility of the inhibition. Moreover, prolonged exposure of the Caco-2 cells to both lignans (up to 7 days) had no effect on P-gp function.

CONCLUSIONS

Phyllanthin and hypophyllanthin directly inhibited P-gp activity and did not interfere with MRP2 activity. It was likely that both phyllanthin and hypophyllanthin could reversibly inhibit P-gp function.

Effects of Phyllanthus amarus on the pharmacokinetics of midazolam and cytochrome P450 activities in rats

Phyllanthus amarus, a commonly used medicinal herb, was investigated for possible herb-drug interactions. The effect on CYP3A-mediated drug metabolism in rats after single dose administration of P. amarus extract was investigated using midazolam (MDZ) as a probe substrate. The effect of multiple dose administration of P. amarus extract on activity and expression of various CYP isoforms were studied. Oral administration of P. amarus extract (800 mg/kg) 1 h before oral MDZ increased the C(max) and AUC(0--∞) of MDZ by 3.9- and 9.6-fold and decreased the clearance by 12%, but did not alter the pharmacokinetics of intravenous MDZ. Daily administration of P. amarus extract (200 or 800 mg/kg/day) for 15 days in rats increased the activity and expression of CYP3A and CYP2B1/2. In contrast, the activities and expressions of CYP1A, CYP2C and CYP2E1 were not significantly changed. The dual effects of P. amarus extract on CYP enzymes were demonstrated. Single dose administration of the extract increased oral bioavailability of MDZ through inhibition of intestinal CYP3A whereas repeated administration of the extract slightly induced hepatic CYP3A and CYP2B1/2 in rats, which suggested that herb-drug interactions by P. amarus may potentially occur via CYP3A and 2B.

Mechanisms of antihyperuricemic effect of Phyllanthus niruri and its lignan constituents

ETHNOPHARMACOLOGICAL RELEVANCE

Phyllanthus niruri Linn. (Euphorbiaceae) is used as folk medicine in South America to treat excess uric acid. Our initial study showed that the methanol extract of Phyllanthus niruri and its lignans were able to reverse the plasma uric acid of hyperuricemic animals.

AIM OF THE STUDY

The study was undertaken to investigate the mechanisms of antihyperuricemic effect of Phyllanthus niruri and its lignan constituents.

MATERIAL AND METHODS

The mechanisms were investigated using xanthine oxidase assay and uricosuric studies in potassium oxonate- and uric acid-induced hyperuricemic rats.

RESULTS

Phyllanthus niruri methanol extract exhibited in vitro xanthine oxidase inhibition with an IC50 of 39.39 microg/mL and a moderate in vivo xanthine oxidase inhibitory activity. However, the lignans display poor xanthine oxidase inhibition in vitro and a relatively weak in vivo inhibitory activity at 10mg/kg. On the other hand, intraperitoneal treatment with Phyllanthus niruri methanol extract showed 1.69 folds increase in urinary uric acid excretion when compared to the hyperuricemic control animals. Likewise, the lignans, phyllanthin, hypophyllanthin and phyltetralin exhibited up to 2.51 and 11.0 folds higher in urinary uric acid excretion and clearance, respectively. The co-administration of pyrazinamide with phyllanthin exhibited a significant suppression of phyllanthin's uricosuric activity resembling that of pyrazinamide with benzbromarone.

CONCLUSIONS

The present study showed that the antihyperuricemic effect of Phyllanthus niruri methanol extract may be mainly due to its uricosuric action and partly through xanthine oxidase inhibition, whereas the antihyperuricemic effect of the lignans was attributed to their uricosuric action.

Analysis of lignans from Phyllanthus niruri L. in plasma using a simple HPLC method with fluorescence detection and its application in a pharmacokinetic study

A simple analytical method using HPLC with fluorescence detection was developed for the simultaneous determination of four lignans, phyllanthin (1), hypophyllanthin (2), phyltetralin (3) and niranthin (4) from Phyllanthus niruri L. in plasma. The method recorded limits of detection for 1, 2, 3 and 4 as 1.22, 6.02, 0.61 and 1.22 ng/ml, respectively, at a signal-to-noise ratio of 5:1 whereas their limits of quantification were 4.88, 24.41, 4.88 and 9.76 ng/ml, respectively, at a signal-to-noise ratio of 12:1. These values were comparable to those of other sensitive methods such as gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography-MS (HPLC-MS) and HPLC-electrochemical detection (HPLC-ECD) for the analysis of plasma lignans. A further advantage over known methods was its simple protocol for sample preparation. The within-day and between-day accuracies for the analysis of the four lignans were between 87.69 and 110.07% with precision values below 10.51%. Their mean recoveries from extraction were between 91.39 and 114.67%. The method was successfully applied in the pharmacokinetic study of lignans in rats. Following intravenous administration, the lignans were eliminated slowly from the body with a mean clearance of 0.04, 0.01, 0.03 and 0.02 l/kg h and a mean half-life of 3.56, 3.87, 3.35 and 4.40 h for 1, 2, 3 and 4, respectively. Their peak plasma concentration upon oral administration was 0.18, 0.56, 0.12 and 0.62 microg/ml, respectively, after 1h. However, their absorption was incomplete with a calculated absolute oral bioavailability of 0.62, 1.52, 4.01 and 2.66% for 1, 2, 3 and 4, respectively.

Determination of four lignans in Phyllanthus niruri L. by a simple high-performance liquid chromatography method with fluorescence detection

A new and simple analytical method using HPLC with fluorescence detection was developed for the simultaneous determination of four lignans (phyllanthin, hypophyllanthin, phyltetralin and niranthin) in Phyllanthus niruri L. plant samples. Optimal separation was achieved with an isocratic mobile phase consisting of acetonitrile-water (55:45 v/v). The method recorded limits of detection (S/N=5) for phyllanthin at 0.61 ng/mL, hypophyllanthin at 6.02 ng/mL, phyltetralin at 0.61 ng/mL and niranthin at 1.22 ng/mL, being 80, 8, 80 and 40 times, respectively, lower when compared with those derived using HPLC-UV detection. The limits of quantification (S/N=12) were 4.88 ng/mL for phyllanthin and phyltetralin, 9.76 ng/mL for niranthin and 24.4 ng/mL for hypophyllanthin showing 40, 8 and 20 times, respectively, lower than those from the UV detection method. The within-day and between-day accuracy for the four lignans were between 98.1% and 102.9% while their precision values were below 2.2%. The mean recovery was between 92.5% and 110.1%. The method was then successfully applied for the quantification of lignans in P. niruri plant samples. The highest amount of lignans was found in the leaves followed by fruits, branches and stem, whilst the roots have the least amount of lignans.