Psidium guajava: a review of its traditional uses, phytochemistry and pharmacology

Suppressive effects of quercetin-3-O-(6″-Feruloyl)-β-D-galactopyranoside on adipogenesis in 3T3-L1 preadipocytes through down-regulation of PPARγ and C/EBPα expression

Obesity is a chronic, costly disease, and flavonoids such as quercetin have been proven to play protective roles against it. This study investigated the suppressive effect of quercetin-3-O-(6″-feruloyl)-β-D-galactopyranoside (QFG) on adipogenesis of 3T3-L1 preadipocytes. Quercetin-3-O-(6″-feruloyl)-β-D-galactopyranoside and quercetin were both extracted from Psidium guajava (Myrtaceae, commonly known as guava) leaves and were evaluated for their suppressive effect on adipogenesis by means of oil red O staining and triglyceride assay. It was shown that QFG inhibited adipogenesis in a dose- and time-dependent manner, and it exerted a stronger effect than did quercetin at the same concentration. Quantitative real-time polymerase chain reaction and western blotting were conducted to further examine the differentiation expression of marker genes and transcriptional factors. Both mRNA and protein expression of the key adipogenic transcriptional factors, peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT (cytidine-cytidine-adenosine-adenosine-thymidine)/enhancer-binding protein alpha (C/EBPα), were inhibited by QFG. Moreover, the mRNA expression patterns of key participants in the Wnt-β-catenin pathway were not altered during the QFG-induced adipogenesis inhibition. These results suggest that QFG effectively suppresses adipogenesis and that it exerts its role mainly through the significant down-regulation of PPARγ and C/EBPα and, probably, via a Wnt-β-catenin independent pathway.

In vitro antimicrobial activity of methanolic leaf extract of Psidium guajava L

AIM

This study was designed to examine the chemical composition and in vitro antimicrobial potential of methanolic extract of Psidium guajava Linn (Myrtaceae).

MATERIALS AND METHODS

The inhibitory effect of methanolic extract of P. guajava was tested against three bacterial and two fungal strains by using the paper disc diffusion method.

RESULTS

The methanolic extract exhibited antibacterial activity against E. coli with minimum inhibitory concentration, 0.78 μg/ml, minimum bactericidal concentration of 50 μg/ml, and appreciable antifungal activity with minimum inhibitory concentration of 12.5 μg/ml. Preliminary phytochemical analysis of methanolic extract revealed the presence of antimicrobial compounds such as flavonoids, steroids, and tannins, which may contribute for the antimicrobial action of P. guajava.

CONCLUSION

The extract was found to be bacteriostatic and fungistatic in action.

Plants used for treating respiratory infections in rural Maputaland, KwaZulu-Natal, South Africa

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional remedies are frequently used in treating various respiratory ailments, and are very important in the primary health care of the people living in rural Maputaland, KwaZulu-Natal, South Africa. Novel information gathered from surveys like the present study is important in preserving indigenous knowledge.

AIM OF THE STUDY

To explore the knowledge that the lay people of a rural community in northern Maputaland have about medicinal plants used in the vicinity to treat respiratory infections.

MATERIALS AND METHODS

Interviews were conducted among 80 homestead inhabitants, using structured questionnaires where convenience sampling was used. The focus was on plants used in treating respiratory infections. Some of the main topics discussed during the interviews were vernacular plant names, plant parts used, harvested amounts, preparation methods, dosage forms and quantities, use of plants in combination as well as the related symptomatic relief associated with respiratory infections.

RESULTS

The study documented 30 plant species (18 families) which are used to treat respiratory infections by the rural people in the study area. Decoctions made with these plants are mostly taken orally, combined with the use of steaming. To the best of our knowledge, Acanthospermum glabratum, Aloe marlothii, Krauseola mosambicina, Ozoroa obovata, Parinari capensis and Plectranthus neochilus are recorded for the first time globally as medicinal plants used for treating respiratory infections and related symptoms. The indigenous aromatic shrub, Lippia javanica was by far the most frequently used plant species, followed by Eucalyptus grandis (an exotic), Tetradenia riparia and then Senecio serratulloides. Twenty-four different plant combinations were used where the most frequently used combination encountered was Eucalyptus grandis with Lippia javanica.

CONCLUSION

The large number of different plant species traditionally used against respiratory infections supports previous research on the importance of traditional medicine in the primary health care of this remote area. The finding of new vernacular plant names and plant uses in the current survey shows the importance of the documentation of such ethnobotanical knowledge.

Recent advances in understanding the antibacterial properties of flavonoids

Antibiotic resistance is a major global problem and there is a pressing need to develop new therapeutic agents. Flavonoids are a family of plant-derived compounds with potentially exploitable activities, including direct antibacterial activity, synergism with antibiotics, and suppression of bacterial virulence. In this review, recent advances towards understanding these properties are described. Information is presented on the ten most potently antibacterial flavonoids as well as the five most synergistic flavonoid-antibiotic combinations tested in the last 6 years (identified from PubMed and ScienceDirect). Top of these respective lists are panduratin A, with minimum inhibitory concentrations (MICs) of 0.06-2.0 μg/mL against Staphylococcus aureus, and epicatechin gallate, which reduces oxacillin MICs as much as 512-fold. Research seeking to improve such activity and understand structure-activity relationships is discussed. Proposed mechanisms of action are also discussed. In addition to direct and synergistic activities, flavonoids inhibit a number of bacterial virulence factors, including quorum-sensing signal receptors, enzymes and toxins. Evidence of these molecular effects at the cellular level include in vitro inhibition of biofilm formation, inhibition of bacterial attachment to host ligands, and neutralisation of toxicity towards cultured human cells. In vivo evidence of disruption of bacterial pathogenesis includes demonstrated efficacy against Helicobacter pylori infection and S. aureus α-toxin intoxication.

An ethnobotanical survey of medicinal plants in the Eastern Himalayan zone of Arunachal Pradesh, India

AIM OF THE STUDY

The medicinal plants are integral source of easily available remedy used in rural healthcare system. This study was conducted among three major ethnic groups namely the Nocte, the Nyishi and the Adi in the Eastern Himalayan region of Arunachal Pradesh to evaluate their comparative knowledge on medicinal plants.

MATERIALS AND METHODS

The three remote districts of Arunachal Pradesh namely the Tirap, the Dibang Valley and the Papum Pare were surveyed through interviewing of randomly selected 237 participants using semi-structured questionnaire and regular field visits to selected districts.

RESULTS

We recorded the traditional use of 74 medicinal plants species belonging to 41 taxonomic plant families used for treating a total of 25 different diseases/ailments. The informant consensus factor (ICF) values demonstrated that local people tend to agree more with each other in terms of the plants used to treat malaria (0.71), jaundice (0.62), urological problems (0.56), dermatological disorders (0.45), pain (0.30), and respiratory disorder (0.33), and while the general health (0.15) and gastro-intestinal disorders category (0.28) were found low ICF values.

CONCLUSION

Of the total 74 species recorded, the highest number of medicinal plants (36 species) was reported from the Adi of Lower Dibang Valley followed by the Nocte of the Tirap (25 species) and the Nyishi ethnic groups of Papum Pare districts (13 species). In the present study, we found that the men, elder people and illiterate ones had better knowledge on medicinal plants as compared to women, younger and literate people. Findings of this documentation study can be used as an ethnopharmacological basis for selecting plants for future phytochemical and pharmaceutical studies.

Biochemical changes in the kidney and liver of rats following administration of ethanolic extract of Psidium guajava leaves

Furtherance to a previous report on the anti-trypanosomal properties of Psidium guajava aqueous leaf extract in rats experimentally infected with Trypanosoma brucei brucei, we have evaluated the effects of the daily intraperitoneal administration of P. guajava leaf extract to rats on the activities of alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and acid phosphatase (ACP) in the kidney, liver and serum. The results obtained revealed that the administration of the extract produced significant increase in the serum activities of AST, ALT, ALP and ACP when compared with the control (p < 0.05). Also AST, ALT and ALP and ACP activities in the tissues of animals administered the extract revealed inconsistent changes (p < 0.05) relative to control. The increase in the serum activity of ALP may be an indicator that there was a likely compromise to the integrity of the plasma membrane as a result of the ethanolic extract administration. This could have caused leakages of the other enzymes investigated, which may explain the corresponding increases in the serum activities of AST, ALT and ACP observed.

Fundamental studies on the inhibitory action of Acanthopanax senticosus Harms on glucose absorption

AIM OF THE STUDY

Acanthopanax senticosus Harms extract (ASE) is used as an ingredient of over-the-counter drugs and functional foods, such as health supplements, in Japan. ASE exhibits a hypoglycemic effect; however, the mechanism of the hypoglycemic effect is not clear. In the present study, we investigated whether ASE has a glucose absorption inhibitory action.

MATERIALS AND METHODS

We examined the effects of ASE on α-amylase and α-glucosidase activities, and on glucose uptake in Caco-2 cells. We also examined the effects of ASE oral administration on glucose tolerance in type 2 diabetes mellitus model db/db mice.

RESULTS

The addition of ASE inhibited α-glucosidase activity but not α-amylase activity. The α-glucosidase inhibitory activity of ASE was approximately 1/13 of that of acarbose. The addition of ASE inhibited 2'-deoxy-D-glucose (DG) uptake in human intestinal Caco-2 cells, and the inhibitory activity of ASE was approximately 1/40 of that of phloretin. Kinetic analysis of glucose uptake indicated that ASE has no effects on DG uptake through passive diffusion, but that ASE inhibits intracellular DG uptake chiefly by inhibiting transport via a glucose transporter. In the glucose tolerance study, db/db mice orally administered ASE for 3 days showed significantly lower plasma glucose level than the control group 30 min after sucrose loading, without affecting plasma insulin levels. In addition, ASE oral administration significantly inhibited α-glucosidase activity in the small intestine mucosa extirpated from the mice.

CONCLUSION

These findings indicate that ASE may be useful as an ingredient of functional foods to improve postprandial hyperglycemia and prevent type II diabetes mellitus.

Ethyl acetate extract of Psidium guajava inhibits IgE-mediated allergic responses by blocking FcεRI signaling

Psidium guajava (P. guajava) is an important food crop and medicinal plant with antioxidant, anti-inflammatory, and anti-allergic activities, supporting its traditional uses. However, its precise effects remain unknown. We investigated the effects of P. guajava ethyl acetate extract (PGEA) on IgE-mediated allergic responses in rat mast RBL-2H3 cells. PGEA reduced antigen (DNP-BSA)-induced release of β-hexosaminidase and histamine in IgE-sensitized RBL-2H3 cells. In addition, it inhibited antigen-induced IL-4 and TNF-α mRNA expression and protein production in IgE-sensitized RBL-2H3 cells. PGEA also suppressed antigen-induced COX-2 mRNA and protein expression in these cells, as well as antigen-induced activation of NFAT and reactive oxygen species. Moreover, it inhibited antigen-induced activation of NF-κB and degradation of IκB-α. To identify the mechanisms underpinning the inhibition of degranulation and cytokine production by PGEA, we examined the activation of intracellular FcεRI signaling molecules. PGEA suppressed antigen-induced phosphorylation of Syk, LAT, Gab2, and PLCγ2 but not Lyn, and inhibited antigen-induced phosphorylation of downstream signaling intermediates including MAP kinases and Akt. Collectively, the anti-allergic effects of PGEA in vitro suggest its possible therapeutic application to inflammatory allergic diseases, in which its inhibition of inflammatory cytokine production and FcεRI-dependent signaling events in mast cells may be hugely beneficial.

An antimicrobial investigation of plants used traditionally in southern Africa to treat sexually transmitted infections

AIM OF THE STUDY

Eighteen plants were assessed for antimicrobial activity against pathogens associated with prevalent urogenital/sexually transmitted infections. Plant selection was based on information obtained from the ethnobotanical literature.

MATERIALS AND METHODS

Dried plant material was submerged in a 1:1 mixture of methanol and dichloromethane for 24 h. Aqueous extracts were prepared by submerging dried plant material in sterile distilled water for 24 h followed by lyophilization. Essential oils were distilled from the two aromatic plant species (Tarchonanthus camphoratus and Croton gratissimus). Antimicrobial activity was assessed using the micro-well minimum inhibitory concentration (MIC) assay with specific modifications to facilitate fastidious growth of pathogens.

RESULTS

Tarchonanthus camphoratus (solvent extract) showed the most significant broad spectrum activity with MIC values ranging between 0.50 and 0.70 mg/ml against five of the six pathogens tested. Other noteworthy activity was found for Hypericum aethiopicum (root) at 0.3 mg/ml (Neisseria gonorrhoeae).Polygala fruticosa and the solvent root extract of Hypericum aethiopicum showed highest sensitivities towards Gardnerella vaginalis at 0.2 mg/ml. Efficacy of the solvent extracts against the pathogen Oligella ureolytica demonstrated antimicrobial activity (MIC values <or=1.0 mg/ml) for seven plant species. The highest activity noted against Ureaplasma urealyticum was for Psidium guajava (solvent extract) at 0.8 mg/ml. In general the aqueous extracts displayed mostly poor anti-STI activity. The most noteworthy susceptibility for the aqueous extracts was noted with the plant extract Syzygium cordatum (MIC value 0.1 mg/ml against Candida albicans). The most noteworthy activity for the essential oils was observed for Tarchonanthus camphoratus (0.8 mg/ml) against Oligella ureolytica.

CONCLUSIONS

Antimicrobial activity was observed for a number of the plant samples against at least one or more pathogen, thus validating the ethnobotanical use as an anti-infective to treat sexually transmitted diseases.

A new perspective on the use of plant secondary metabolites to inhibit methanogenesis in the rumen

Recently, greenhouse gas emissions have been of great concern globally. Ruminant livestock due to production of methane during normal fermentation in the rumen contributes substantially to the greenhouse effects. During the recent decade, a paradigm shift has been initiated whether plant secondary metabolites (PSM) could be exploited as natural safe feed additives alternative to chemical additives to inhibit enteric methanogenesis. More than 200,000 defined structures of PSM have been known. Some plants or their extracts with high concentrations of bioactive PSM such as saponins, tannins, essential oils, organosulphur compounds, flavonoids and many other metabolites appear to have potential to inhibit methane production in the rumen. The possible mechanisms and effects of many PSM on rumen methanogenesis are not clearly understood. Saponins may decrease methanogenesis through the inhibition of rumen protozoa and in turn may suppress the numbers and activity of methanogens. Although the direct effect of saponins on methanogens has not been demonstrated, saponins might inhibit methanogens at high doses. Tannins may inhibit the methanogenesis directly and also via inhibition of protozoal growth. Essential oils, organosulphur compounds and flavonoids appear to have direct effects against methanogens, and a reduction of protozoa associated methanogenesis probably plays a minor role for these metabolites. The chemical structure and molecular weight of the PSM and chemical composition of diets dependent upon the different feeding regimes may influence the effects of PSM on methane production. Although PSM may negatively affect nutrient utilization, there is evidence that methanogenesis could be suppressed without adversely affecting rumen fermentation, which could be exploited to mitigate methane emission in ruminants.

Medicinal plants used for the treatment of diarrhoea in northern Maputaland, KwaZulu-Natal Province, South Africa

AIM OF THE STUDY

To document the ethnobotanical knowledge on antidiarrhoeal plant use by lay people in a rural community in northern Maputaland.

MATERIALS AND METHODS

Interviews were conducted amongst homestead inhabitants, using structured questionnaires. The focus was on the medicinal plants which are growing in and around the immediate vicinity of the homesteads.

RESULTS

Twenty-three plant species are used in the study area to treat diarrhoea. Four plants (Acacia burkei, Brachylaena transvaalensis, Cissampelos hirta and Sarcostemma viminale) are recorded for the first time globally as an antidiarrhoel. The three antidiarrhoeal plants most frequently used in the study area are Psidium guajava, Catharanthus roseus and Melia azedarach (all three are exotic to South Africa), followed by Sclerocarya birrea and Strychnos madagascariensis which are indigenous. Seven of the 23 plant species are used in five different plant combinations for increased antidiarrhoeal efficacy.

CONCLUSION

The wide variety of plants that are used to treat diarrhoea in this area supports the traditional value that medicinal plants have in the primary health care system of the rural people in northern Maputaland, KwaZulu-Natal.

Newer insights into the mechanism of action of Psidium guajava L. leaves in infectious diarrhoea

BACKGROUND

Psidium guajava L., Myrtaceae, is used widely in traditional medicine for the treatment of diarrhoea, dysentery, gastroenteritis, stomachaches, and indigestion. However, the effect of the leaf extract of P. guajava on the pathogenesis of infectious diarrhoea has not been studied. The present study evaluates the effect of a hot aqueous extract (decoction) of dried leaves of P. guajava on parameters associated with pathogenicity of infectious diarrhoea. The aim was to understand its possible mechanism(s) of action in controlling infectious diarrhoea and compare it with quercetin, one of the most reported active constituents of P. guajava with antidiarrhoeal activity.

METHODS

The crude decoction and quercetin were studied for their antibacterial activity and effect on virulence features of common diarrhoeal pathogens viz. colonization of epithelial cells and production and action of enterotoxins. Colonization as measured by adherence of enteropathogenic Escherichia coli (EPEC) and invasion of enteroinvasive E. coli (EIEC) and Shigella flexneri was assessed using HEp-2 cell line. The production of E. coli heat labile toxin (LT) and cholera toxin (CT) and their binding to ganglioside monosialic acid (GM1) were studied by GM1-ELISA whereas the production and action of E. coli heat stable toxin (ST) was assessed by suckling mouse assay.

RESULTS

The decoction of P. guajava showed antibacterial activity towards S. flexneri and Vibrio cholerae. It decreased production of both LT and CT and their binding to GM1. However, it had no effect on production and action of ST. The decoction also inhibited the adherence of EPEC and invasion by both EIEC and S. flexneri to HEp-2 cells. Quercetin, on the other hand, had no antibacterial activity at the concentrations used nor did it affect any of the enterotoxins. Although it did not affect adherence of EPEC, it inhibited the invasion of both EIEC and S. flexneri to HEp-2 cells.

CONCLUSION

Collectively, the results indicate that the decoction of P. guajava leaves is an effective antidiarrhoeal agent and that the entire spectrum of its antidiarrhoeal activity is not due to quercetin alone.

Ethnopharmacological use of herbal remedies for the treatment of malaria in the Dangme West District of Ghana

AIM OF STUDY

Malaria is one of the most important diseases in the world. Because of the devastating nature of the disease there is an urgent need to develop new drugs or vaccines for the treatment, prevention and management of the disease. The objective of the present study was to collect and document information on herbal remedies traditionally used for the treatment of malaria in the Dangme West District of Ghana.

METHODS

Data was collected from 67 indigenous households in ten communities in the district using a validated questionnaire.

RESULTS

In total, 30 species of plants belonging to 28 genera in 20 families were reported to be used in the preparation of the herbal remedies. Mature leaves were the most (55%) common plant part used and 73.3% of the herbal remedies involved a single plant. Most of the herbal remedies were prepared by boiling and administered orally. The majority (47%) of the species of plants used were collected from their compounds or home gardens.

CONCLUSIONS

Knowledge about malaria and treatment practices exists in the study area. Herbal remedies were commonly used by people for the treatment of malaria because they were cost-effective. They are also more accessible. Many of the species of plants used have been documented for the treatment of malaria as well as investigated for their phytochemical and antimalarial and/or antiplasmodial activity confirming the results of previous studies as well as rationalization of their traditional use. Five species of plants used in the study area, namely, Bambusa vulgaris Schrad. ex J.C. Wendl. (Poaceae), Deinbollia pinnata Schum. &Thonn. (Sapindaceae), Elaeis guineensis Jacq. (Arecaceae), Greenwayodendron sp. (Annonaceae) and Solanum torvum Sw (Solanaceae), are documented for the first time for their use in the treatment of malaria. "The result of this study provides the basis for further pharmacological studies on the herbal remedies used".

Artocarpus: a review of its traditional uses, phytochemistry and pharmacology

The genus Artocarpus (Moraceae) comprises about 50 species of evergreen and deciduous trees. Economically, the genus is of appreciable importance as a source of edible fruit, yield fairly good timber and is widely used in folk medicines. The aim of the present review is to present comprehensive information of the chemical constituents, biological and pharmacological research on Artocarpus which will be presented and critically evaluated. The close connection between traditional and modern sources for ethnopharmacological uses of Artocarpus species, especially for treatment against inflammation, malarial fever, diarrhoea, diabetes and tapeworm infection. Artocarpus species are rich in phenolic compounds including flavonoids, stilbenoids, arylbenzofurons and Jacalin, a lectin. The extracts and metabolites of Artocarpus particularly those from leaves, bark, stem and fruit possess several useful bioactive compounds and recently additional data are available on exploitation of these compounds in the various biological activities including antibacterial, antitubercular, antiviral, antifungal, antiplatelet, antiarthritic, tyrosinase inhibitory and cytotoxicity. Several pharmacological studies of the natural products from Artocarpus have conclusively established their mode of action in treatment of various diseases and other health benefits. Jacalin, a lectin present in seeds of this plant has a wide range of activities. Strong interdisciplinary programmes that incorporate conventional and new technologies will be critical for the future development of Artocarpus as a promising source of medicinal products. In the present review, attempts on the important findings have been made on identification; synthesis and bioactivity of metabolites present in Artocarpus which have been highlighted along with the current trends in research on Artocarpus.

Tamarindus indica L. (Fabaceae): patterns of use in traditional African medicine

To increase the understanding of the ethnopharmacology of a single species, elaboration of dispersed primary data is required. Tamarindus indica L. (Fabaceae), or tamarind, is a common tree, especially in West Africa, with a good potential to contribute to affordable local health care based on traditional medicine (TM). For this single species review, more than 60 references with detailed information on the ethnopharmacology of Tamarindus indica in the African context were selected. It showed that most prominently, the fruits are used as laxative or febrifuge throughout the Sahel and Soudan ecological zones. Tamarind bark and leaves are often involved in the treatment of wounds, especially in central West Africa. While the bark is used to treat diarrhoea in West Africa, the leaves are used for this purpose in East Africa. Our findings suggest a difference in the way tamarind is used between East and West Africa and we assess the similarities of its uses within those regions. This review demonstrates the capability of literature research to reveal knowledge by mining and compiling information from the growing body of primary ethnopharmacologic data, much of which is published in this journal. By creating a specific profile of tamarind in the context of traditional medicine throughout Africa, the authors contribute to the collection of current ethnobotanic species accounts on Tamarindus indica that tend to be qualitative and more general.

Anti-hyperglycemic and anti-hyperlipidemic effects of guava leaf extract

Psidium guajava Linn. (guava) is used not only as food but also as folk medicine in subtropical areas around the world because of its pharmacologic activities. In particular, the leaf extract of guava has traditionally been used for the treatment of diabetes in East Asia and other countries. Moreover, the anti-hyperglycemic activity of the extract has been reported in some animal models. However, little is known regarding the therapeutic activity of the extract in human clinical trials as well as its underlying therapeutic mechanisms and safety. In Japan, Guava Leaf Tea (Bansoureicha^®, Yakult Honsha, Tokyo, Japan) containing the aqueous leaf extract from guava has been approved as one of the Foods for Specified Health Uses and is now commercially available. This review describes the active component of the aqueous guava leaf extract and its inhibition of alpha-glucosidase enzymes in vitro, safety of the extract and Guava Leaf Tea, reduction of postprandial blood glucose elevation, and improvement of hyperglycemia, hyperinsulinemia, hypoadiponectinemia, hypertriglycemia and hypercholesterolemia in murine models and several clinical trials. It is suggested that the chronic suppression of postprandial blood glucose elevation is important in preventing type 2 diabetes mellitus, and that Guava Leaf Tea is considered useful as an alimentotherapy for chronic treatment.

Two new benzophenone glycosides from the fruit of Psidium guajava L

The ripe edible fruits of Psidium guajava L. was phytochemically investigated, three benzophenone glycosides, 2, 6-dihydroxy-3, 5-dimethyl-4-O-beta-D-glucopyranosyl-benzophenone (1), 2, 6-dihydroxy-3-methyl-4-O-(6''-O-galloyl-beta-D-glucopyranosyl)-benzophenone (2), 2, 6-dihydroxy-3, 5-dimethyl-4-O-(6''-O-galloyl-beta-D-glucopyranosyl)-benzophenone (3) were isolated by means of chromatography, and their structures were elucidated on the basis of mass spectrometry, (1)H NMR, (13)C NMR, HSQC and HMBC data. Compounds 1 and 2 were new benzophenone glycosides, and here we report the complete spectroscopic assignments for 3.

Effect of guava (Psidium guajava L.) leaf extract on glucose uptake in rat hepatocytes

People in oriental countries, including Japan and Taiwan, boil guava leaves (Psidium guajava L.) in water and drink the extract as a folk medicine for diabetes. The present study investigated the enhancement of aqueous guava leaf extract on glucose uptake in rat clone 9 hepatocytes and searched for the active compound. The extract was eluted with MeOH-H(2)O solutions through Diaion, Sephadex, and MCI-gel columns to separate into fractions with different polarities. The uptake test of 2-[1-(14)C] deoxy-D-glucose in rat clone 9 hepatocytes was performed to evaluate the hypoglycemic effect of these fractions. The active compound was identified by nuclear magnetic resonance analysis and high-performance liquid chromatography (HPLC). The results revealed that phenolics are the principal component of the extract, that high polarity fractions of the guava leaf extract are enhancers to glucose uptake in rat clone 9 hepatocytes, and that quercetin is the major active compound. We suggest that quercetin in the aqueous extract of guava leaves promotes glucose uptake in liver cells, and contributes to the alleviation of hypoglycemia in diabetes as a consequence.