Preliminary Research On Antifungal Activity Of The Peel Of Punica Granatum Linn

It is a focus for the study of botanical pesticides to find natural bio-active from plants. To isolate these compounds and to make use of them as new agrochemicals or leading structure of new agrochemicals is one of the hot spots now.Pomegranate (Punica granatum) peel, a kind of traditional medicine herb that can be used in clinical medicine, has rarely used in agriculture as fungicide. In this paper, extracts of pomegranate peel were tested for its antimicrobial activities on Fusarium oxysporum f. cucumerinum. The processing conditions of active substances extraction from pomegranate peel such as the temperature and time of extracting were optimized with orthogonal experimental design method. The sensitivity to universal factors of the extract was studied. At the same time, the isolation and purification of the antimicrobial components of pomegranate were also accomplished. The main results were as follows.Five solvents (petroleum ether, methanol, chloroform, ethyl acetate, and n-hexane) were used to extract plant samples, and the extracts were tested for their fungicidal activities against F. oxysporum by means of growth rate method. The results showed that pomegranate peel extracts using different polar solvents had different inhibition rates on F. oxysporum. The antimicrobial activities of the extract increased with the increasing of polarity of solvent. At the concentration of 100 g /L, the inhibition effect of methanol extract was best (82.5%), followed by chloroform and acetic ether extracts (75.1% and 71.63%). Hexane and petrolism ester extracts were worst (62.53% and 61.93%). The EC50 (g/L) of the extract from each solvent was 15.73, 22.32, 34.68, 54.27 and 37.91, respectively. The optimum conditions of active substances extraction were as follows: the concentration of methanol at 70%, temperature for extracting at 45°C, the ratio of material to solvent at l:20, extraction time at 30 minutes with 3 times. Under this condition combination the antimicrobial inhibition rate was 68.55 %.Methanol extracts of pomegranate were isolated by means of phytochemistry combined with bioassay. Methanol extracts were continuously extracted by petroleum ether, chloroform, ethyl acetate and n-butyl alcohol. The n-butyl alcohol extract possessed the highest activities to four phytopathogenic fungi with the inhibition rate >70% at the concentration of 200 g/L. The highest inhibition rate against Rhizoctonia solani reached 90.67% with the EC50 at 26.2 g/L. The n-butyl alcohol extract was further isolated and purified by thin-layer chromatography (TLC) and column chromatography. Three components (PGP10, PGP15 and PGP7') demonstrating high bioactivity might be alcohols, alkenes, esters, phenols and pseudopelletierine as determined by LC-MS and GC-MS.By screening of solvents and emulsifier, we prepared a 25% SL of pomergranate peel and tested it in greenhouse pot efficacy experiments. The results showed bioactivity for the control of F. oxysporum, Botrytis cinerea and Bipolaris maydis. The efficacy of the 25% SL of pomegranate peel at 1:100 dilution was 86.62% against B. maydis that was better than carbendazol at 1:300 dilution, 73.01% against F. oxysporum that was similar as carbendazol at 1:300 dilution, and 77.28% against B. cinerea that was similar as thiophanate methyl at 1:300 dilution.