PHYTOCHEMICAL ANALYSIS, ANTIOXIDANT AND ANTIMICROBIAL ACTIVITIES OF ENDOPHYTIC FUNGI FROM WATERMELON (Citrullus lanatus L.)RIND AND SEED

Abstract

Watermelon is one of the major utilized fruits grown in the warmer part of the world. The juice or pulp from watermelon is used for human utilization, while rind and seeds are major solid wastes. Endophytic microbes have been an important and potential resource of bioactive compounds. The present study was undertaken to assess phytochemical analysis, antioxidant and antimicrobial activities of endophytic fungal isolates from water melon seeds and fruit rind. The watermelon seed and rind samples were surface sterilized before used as endophytic fungal culture. Fungal culturing and identifications of genera were made according to fungal identification manual. Then, the crude endophytic fungal extracts were prepared using methanol as a solvent. The qualitative screening of phytochemical was made. The antioxidant activity was conducted based on determination of phenolic content, DPPH and hydrogen peroxide free radical scavenging activities. The antimicrobial activity test was tested based on disc diffusion method and broth dilution methods. The macroscopic colony appearance and microscopic morphological structures of the pure cultures of the endophytic fungal isolates of watermelon rind and seed were revealed three isolates obtained from watermelon seed, Similarly, three isolates were recorded from watermelon rind.Trichoderma sp has presented significantly the highest phenolic content (11.44mg/mL), then followed by Aspergillus sp(11.15mg/mL) and Fusarium sp1 (10.45mg/mL).significantly the highest DPPH (52.92%) was recorded for Aspergillus sp followed by Penicillium sp isolate extract (49.91%). Significantly the highest hydrogen peroxide scavenging activities (53.12%) was recorded for Penicillium sp methanolic extract. The antibacterial activity of the highest concentration of the extract (200mg/ml) of the crude extracts has recorded mean zone of inhibition ranging from 16.40 to 30.77 mm against both gram positive and gram negative bacterial test pathogens. The antifungal activity of the highest concentration of the extract (200mg/ml) has presented the mean zone of inhibition ranging from 22.00 to 31.77mm. The endophytic fungal extract presented the strongest antibacterial activity with MIC (1.17mg/ml) and corresponding MBC (1.17mg/ml) for Penicillium sp extract against S. aureus. Whilst, the weakest antibacterial activity with MIC (37.5mg/ml) and corresponding MBC (50mg/ml) were recorded for Fusarium sp2 isolate extract against both E. coli and S. aureus