Biologically active secondary metabolites of an endophytic fungus of Psidium guajava

Onyeka Chinwuba Obidiegwu Onyeka Chinwuba Obidiegwu,Festus Basden Chiedu Okoye Festus Basden Chiedu Okoye,Keziah Uchechi Ajah Keziah Uchechi Ajah,Chika Christiana Abba Chika Christiana Abba,Nonye Treasure Ujam Nonye Treasure Ujam

doi:10.30574/gscbps.2022.18.1.0023

Onyeka Chinwuba Obidiegwu Onyeka Chinwuba Obidiegwu, Festus Basden Chiedu Okoye Festus Basden Chiedu Okoye + Show 3 more

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https://doi.org/10.30574/gscbps.2022.18.1.0023

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Abstract

Endophytes possess several phytohormones and bioactive metabolites of medicinal importance and thus, continue to generate research interest as candidates in drug discovery programmes. This study was carried out to investigate the secondary metabolites of an endophytic fungus isolated from leaves of Psidium guajava. Endophytic fungal isolation, fungal fermentation; and extraction of secondary metabolites in ethyl acetate were carried out using standard methods. The crude extract was subjected to Vacuum Liquid Chromatography (VLC) using binary combinations of Hexane:Ethyl acetate and Dichloromethane:Methanol to obtain fourteen sub-fractions designated PG55-1 to PG55-14. The fungal crude extracts and VLC sub-fractions were screened for antimicrobial activity and were also subjected to high-performance liquid chromatography-diode-array detection (HPLC-DAD) analysis for the identification of bioactive compounds. An endophytic fungus, PG55 was isolated from the leaf of Psidium guajava. The fungal secondary metabolites showed antibacterial properties, with minimum inhibitory concentrations ranging from 0.0625 – 1 mg/ml. No antifungal activity was observed. HPLC-DAD analysis of the extract suggested the presence p-hydroxybenzoic acid, pentenedioic acid and palitantin in one of the fractions of PG55. Some of these compounds are known antimicrobial agents and may be responsible for the antimicrobial activities recorded for the fungal extracts. The results of this study, suggests the many potentials possessed by Nigerian plants as hosts of endophytes that could be reservoirs for excellent sources of pharmacologically active compounds.

Highlights

Endophytes have recently generated significant interest in the microbial chemistry community due to their immense potential to contribute to the discovery of new bioactive compounds
The fungal crude extracts and Vacuum Liquid Chromatography (VLC) sub-fractions were screened for antimicrobial activity and were subjected to highperformance liquid chromatography-diode-array detection (HPLC-Diode Array Detection (DAD)) analysis for the identification of bioactive compounds
Culture media used in this study include: fungal isolation and purification medium [Malt Extract Agar (MEA) (Oxoid, UK)], fermentation medium [Rice medium (Rice-100 g + 110 mL of distilled water)], antimicrobial assay media [Mueller Hinton Agar (MHA) and Sabouraud Dextrose agar (SDA) (Oxoid, UK)]

Summary

Introduction

Endophytes have recently generated significant interest in the microbial chemistry community due to their immense potential to contribute to the discovery of new bioactive compounds. The symbiotic nature of this relationship indicates that endophytic bioactive compounds are likely to possess reduced cell toxicity, as these chemicals do not kill the eukaryotic host system. This is of significance to the medical community as potential drugs may not adversely affect human cells [2]. Endophytes are chemical synthesizer inside plants [3], in other words, they play a role as a selection system for microbes to produce bioactive substances with low toxicity toward higher organisms [1]

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