Study On The Antimicrobial Ingredients Of Picrasma Quassioides

Picrasma quassioides is widely distributed around the world,and mainly distributed in southern provinces in China.P.quassioides is a traditional Chinese medicine and has a wide range of medicinal bioactivities.However,its application in agriculture was rarely reported.In this paper,guided by biological activity tracking,the antimicrobial compounds were isolated from P.quassioides by using silica gel column chromatography,gel filtration chromatography,and prep-HPLC techniques.Their chemical structures were identified by NMR and MS analysis.The antimicrobial activities of the obtained five alkaloids against 12species of plant pathogenic fungi and 3 species of plant pathogenic bacteria were evaluated.The extraction process of alkaloids from P.quassioides were studied thoroughly.In this paper,all together 9 compounds were isolated from the plant by various chromatography techniques.Based on the spectral data,they were identified as canthin-6-one（1）nigakinone（2）4,5-dimethoxycanthin-6-one（3）1-methoxycarbonyl-β-carboline（4）1-methoxyl-3-methoxycarbonyl-β-carboline（5）,daidzein（6）,formononetin（7）,6-methoxy-7,8-methylenedioxygen coumarin（8）,and physalis D（9）.Compound 6,7and8 was isolated from P.quassioides for the first time,and compound 5 was firstly reported as a natural product.In this study,the antifungal and antibacterial activity of P.quassioides against a panel of plant pathogenic fungi and bacteria were evaluated by using mycelial growth rate method,filter paper diffusion method,detached twig assays in laboratory to evaluate.The obtained alkaloids showed good antifungal activity against the tested microorganisms.Canthin-6-one（1）,among five alkaloids,has the best antifungal effect,and its EC₅₀ against 12 plant pathogenic fungi ranged from 1.49 mg/L to 8.80 mg/L.V.mali is the most sensitive species to canthin-6-one,and its EC₅₀ was 1.49 mg/L.The antibactrial activity of canthin-6-one against tested bacteria to is comparable to streptomycin sulphate.The extract of P.quassioides also showed good in vivo antifungal activity,and can effectively control apple valsa canker and apple anthracnose diseases.At 2500 mg/L,The protective and therapeutic effects of the extract on apple valsa canker are 88.73%and 95.67%,respectively.The therapeutic and protective effects of canthin-6-one at 1000mg/L on apple anthracnose are above 70%,and the efficiency on apple valsa canker is over 80%.The extraction process of the alkaloids from P.quassioides were studied.The optimum extraction conditions were established based on the recovery of the active ingredients.The suitable solvent is 80%methanol,and reflux extraction is superior to other ways of extraction.In this study,the antifungal activity of five alkaloids from P.quassioides was comprehensively evaluated,and the extraction process of the alkaloids from P.quassioides was studied.The results showed that P.quassioides is a potent resource for the development of botanical fungicides.