Chemical constituents of Psidium guajava leaves and their antibacterial activity

Three new flavonoid glycosides isolated from Pteridium aquilinum

Three new flavonoid glycosides, (S)-4',6,8-trihydroxyflavanone-7-C-glucoside (1), (R)-4',6,8- trihydroxyflavanone-7-C-glucoside (2) and distenin-7-O-β-D-glucoside (3), along with nine known flavonoids (4-12) were isolated from the aerial of Pteridium acquilinum. Their structures were elucidated by the analysis of spectroscopy data and their comparison with the reported values. The two C-glycosyl flavanones (1 and 2), were isolated from this specie, which might be chemotaxonomic markers of this specie. In addition, three new flavonoids were preliminarily examined for their anti-inflammatory activity. Compounds 1-3 inhibited the NF-κB induction by 46.3%, 59.6% and 29.2%, respectively.

Psidium guajava: An Insight into Ethnomedicinal Uses, Phytochemistry, and Pharmacology

BACKGROUND

Psidium guajava (guava) is widely distributed in tropical and subtropical regions and adapted to various environmental conditions. Guava is an important economic fruit widely used as food and folk medicine. It contains flavonoids, alkaloids, tannins, triterpenoids, reducing sugars, essential oils, carotenoids, polyphenols, etc. The presence of triterpenoid acids such as guavacoumaric, ursolic, jacoumaric, guajavanoic, guavenoic, and Asiatic acids helps to develop novel drugs against various diseases. It is used traditionally for medicinal purposes, mainly for antioxidant, antimicrobial, antispasmodic, antidiabetic, anticancer, antiallergy, anti-inflammatory, and hepato-protective properties.

OBJECTIVE

The systematic literature study aims to summarize its botanical description, phytochemicals, pharmacological activities, and clinical trials. This review focuses on the plant's chemical composition and scientific approaches to human welfare.

METHODS

A systematic literature search was done on Psidium guajava through previous literature and online databases such as Google Scholar, Pubmed, Science Direct, etc., to explain its ethnomedicinal uses, phytochemistry, and pharmacological applications.

RESULTS

Previous literature studies of Psidium guajava suggest it can serve as antioxidant, antimicrobial, antispasmodic, antidiabetic, anticancer, anti-allergy, anti-inflammatory, and hepatoprotective effects. Successful clinical trials performed on the plant extracts against infantile rotaviral enteritis and infectious gastroenteritis showed future directions to work with the plant for clinical applications.

CONCLUSION

In this review, an attempt is made to show all literature studied, especially in phytochemistry, pharmacology, clinical trials and uses as traditional folk medicine around the world. The leaves have been used by folklore over the years to treat various ailments such as skin ulcers, diarrhoea, vaginal irritation, cough, conjunctivitis, etc. Further studies are required to explore more therapeutic remedies and to develop new medicines for future perspectives.

Antimicrobial Activity of Psidium guajava Aqueous Extract against Sensitive and Resistant Bacterial Strains

The inappropriate use of antimicrobials, along with environmental conditions, can lead to the emergence of resistant microorganisms. The use of phytopharmaceuticals and herbal medicines has a positive impact and represents a promising alternative. Psidium guajava extracts have been widely reported to have antimicrobial potential; however, studies reporting their activity against resistant bacterial strains are scarce. Because of the emerging resistance, the aim of this study was to analyze the antimicrobial capacity of the aqueous extract of guava leaves against wild-type and resistant bacterial strains. The aqueous extract obtained from the leaves of P. guajava was evaluated by HPLC for the content of total phenolics and tannins, antioxidant activity, and chemical composition. The antimicrobial activity of the extracts was analyzed by the disk diffusion and broth microdilution methods. The results of the chemical analysis of the extracts showed total phenolics content of 17.02 ± 6.87 mg/g of dry extract, total tannin content of 14.09 ± 1.20 mg of tannic acid equivalents/g of dry extract, and moderate antioxidant capacity with an EC₅₀ value of 140 µg/mL. Flavonoids are the major compounds (rutin, hesperidin, and quercetin), followed by phenolic acids. Disk diffusion test results showed the presence of inhibition halos for Gram-positive bacteria (Staphylococcus aureus, sensitive and resistant; Staphylococcus pseudintermedius, sensitive and resistant; and Streptococcus spp., beta-hemolytic), while for Gram-negative bacteria (Escherichia coli, sensitive and resistant), there was no inhibition in the tested concentration range. The Minimal Inhibitory Concentration was 6.8 mg/mL for all Gram-positive strains evaluated. The present study demonstrated the antimicrobial activity of the aqueous extract of P. guajava against sensitive and resistant Gram-positive bacteria. The better antimicrobial activity found in the present study compared with previously reported activity should be highlighted and may be related to the higher concentration of total phenolics present in the tested extract. Moreover, the content of tannins found suggests a species with high quality that produces tannins. These new findings suggest an innovative profile regarding therapeutic resources that can be adopted to combat resistant microbial strains.

Cytotoxicity, oral toxicity, genotoxicity, and mutagenicity evaluation of essential oil from Psidium glaziovianum Kiaersk leaves

ETHNOPHARMACOLOGICAL RELEVANCE

Members of the Psidium genus have been suggested in ethnobotanical research for the treatment of various human diseases, and some studies have already proven their popular uses through research, such as Psidium glaziovianum, which is found in Brazil's northeast and southeast regions and has antinociceptive and anti-inflammatory properties; however, the safety of use has not yet been evaluated.

AIM OF THE STUDY

This study investigated the safety of using essential oil obtained from P. glaziovianum leaves (PgEO) in vitro and in vivo models.

MATERIALS AND METHODS

Cytotoxicity was evaluated in murine erythrocytes, while acute toxicity, genotoxicity (comet assay) and mutagenicity (micronucleus test) studies were performed using Swiss albino mice.

RESULTS

In the cytotoxicity assay, the hemolysis rate indicated a low capacity of PgEO to cause cell lysis (0.33-1.78%). In the acute oral toxicity study, animals treated with up to up to 5000 mg/kg body weight did not observe mortality or physiological changes. Neither dosage caused behavioral problems or death in mice over 14 days. The control and 2,000 mg/kg groups had higher feed intake and body weight than the 5,000 mg/kg PgEO group. Erythrocyte count, hemoglobin level, mean corpuscular volume, and MCV decreased, but serum alanine and aspartate aminotransferases increased. In the genotoxic evaluation, 5000 mg/kg PgEO enhanced nucleated blood cell DI and DF.

CONCLUSIONS

The present study describes that PgEO can be considered well tolerated in acute exposure at doses up to 2000 mg/kg, however the dose of 5000 mg/kg of PgEO should be used with caution.