EFFECTS OF ACTIVE PHYTOCHEMICALS OF PROSOPIS JULIFLORA AS ANTI-SPOILING AGENTS OF POSTHARVEST FRUITS

Abstract

Global increase in food demand has made the fresh produce spoilage a worldwide concern. Adverse effects of commercial spoilage control agents on human health and on the environment are major public concern. In this study, Prosopis juliflora fruit and leaf extracts were studied for their antimicrobial activities against the growth of selected bacteria (Escherichia. coli, Bacillus subtilis, Staphylococcus aureus, Proteus mirabilis, and Pseudomonas aeruginosa), yeast (Candida albicans), and fungi (Aspergillus niger, Penicillium chrysogenum, Botrytis cinerea, Fusarium oxysporum, Alternaria alternata,Penicillium citrinum, Colletotrichum gloeosporioides, Cladosporium cladosporioides, and Geotrichum candidum). The novel P. juliflora water-soluble leaf ethanolic (PJ-WSLE) extract showed the highest antibacterial activity. The potential effect of PJ-WS-LE extract coating on the extension of fruits' shelf-lives and in maintaining storage parameters were evaluated in addition to the genetic variation of the invasive P. juliflora species in Qatar. PJ-WS-LE extract was fractionated using FPLC in order to identify active phytochemicals. Antimicrobial tests showed total inhibition of B. cinerea, A. alternata, B. subtilis, S. aureus and C. albicans with MICs ranging between 0.125 mg/ml and 1mg /ml. Even fungal strains that were the least affected showed alterations in their hyphae and spores exposed to PJ-WS-LE extract when observed using scanning electron microscope (SEM). PJ-WS-LE extract showed high efficacy in protecting inoculated cherry tomato samples from A. alternata and B. cinerea infections. PJ-WS LE extract alone extended strawberries shelf-life at 4°C by 2.32 folds and maintained the best storage quality-parameters when embedded in 1% chitosan. On mangoes, 8 mg/ml of PJ-WS-LE extract has 80% efficacy in controlling A. alternata infection and it lowers C. gloeosporioides disease severity by 53.4%. PJ-WS-LE extract at 8mg/ml showed also efficacy in increasing cucumber shelf-life at 22°C by 77%. P. juliflora did not show genetic variation in Qatar and extracts of leaves collected from various locations showed the same antimicrobial activities. Fractionation purification method allowed the successful identification of one biologically active fraction that has high thermostability. In conclusion, PJ-WS-LE extract is a natural antifungal agent that can replace common anti-spoiling chemicals in field and protect vegetables and fruits at post-harvest stage.