Abstract
Pumpkin peel is a by-product which may contain some bioactive compounds. It should be of interest to investigate the efficacy of pumpkin peel to control postharvest disease. Anthracnose disease caused by Colletotrichum musae is a major postharvest disease and causes loss of banana in Thailand. The aims of this research were to investigate antioxidant activity and bioactive compounds in pumpkin peel and to investigate the antifungal activity of pumpkin peel crude extract against anthracnose in banana. Pumpkin peel (Cucurbita spp.) was extracted with three different solvents: methanol, ethanol and acetone in ratio of pumpkin peel to solvent at 1:5 (w/v). Methanol was the best solvent for extraction, showing the significant higher (P ≤ 0.05) values of DPPH (19.57 µmol TE / 100 g DW), FRAP (64.88 µmol Fe(ll) / 100 g DW) and total phenolic content (92.25 mg GAE / 100 g DW), when compared with ethanol and acetone. Methanol at the concentrations of 95%, 70% and 50% were then used for extraction in a subsequent trial. The result showed that 50% methanol gave a significant higher (P ≤ 0.05) yield, DPPH (40.73 µmol TE / 100 g DW), FRAP (97.15 µmol Fe(ll) / 100 g DW) and phenolic compound (202.43 mg GAE / 100 g DW) when compared with 95% and 70% methanol. The 50% methanol pumpkin peel crude extract was then diluted to 95%, 70% and 50% for antifungal assays, both in vitro and in vivo. The methanol pumpkin peel extract at all concentrations significantly delayed (P ≤ 0.05) radial growth of C. musae during incubation for 6 days in comparison with the control (dimethyl sulfoxide: DMSO). There was no significant difference between methanol pumpkin peel extracts and control (DMSO) in rot lesion development on banana during storage for 5 days. Although, pumpkin peel extract did not control banana anthracnose, it might be used in combination with fungicide. And hence, the use of chemical would possibly be reduced.
