Allelopathy On Bamboo Grass Leaves And Isolation Of Allelochemicals From Shibataea Chinensis Nakai Leaf

Development of new environment-friendly pesticide by using allelochemicals is a promising new research area for improving the quality and safety of agricultural products. It is well known and of great concern that in the bamboo forest land weeds are hard to grow. Bamboo leaf is rich in secondary metabolites. It is of great practical significance to explore new allelochemicals for botanical herbicides from bamboo leaf. Bamboo grasses have rapid growth rate, lush foliage and are easy to harvest. Therefore, they have the potential to be developed as a kind of leafy bamboo grove. The allelopathy of bamboo leaves from 9 species were evaluated by a bioassay with Lactuca sativa L. and Cucumis sativus L as the targets. Then, the most representative and potential Shibataea chinensis Nakai was selected. Its effective parts of the selected bamboo grass were screened by detecting the active components content and related chemical compounds. And finally, the study of allelopathy of the effective parts and active chemical compounds from Shibataea chinensis Nakai leaf was carried out. The main conclusions are as follows:(1) The content of secondary metabolites and allelopathy of the above nine bamboo grasses leaves were compared. The result shows that the bamboo grasses(Shibataea chinensis Nakai, Shibataea nanpingensis Q. F. Zheng et K. F. Huang, Pleioblastus kongosanensis f. aureostriatus Muroi et Yuk. Tanaka, Pleioblastus chino f. kimmei, Sasa fortunei(Van Houtte) Fiori, Sasa argenteastriatus E.G.Camus, Sasa glabra f. alba-striata Muroi, Sasa auricoma E.G.Camus, Indocalamus decorus Q. H. Dai leaves are rich in secondary metabolites, i.e, total phenolic, total flavonoids and titerpenoids. Among 14 species bamboo leaf, Shibataea chinensis Nakai contains higher total phenolic(8.21 %), total flavonoids(4.22 %) and titerpenoids(0.93 %) content than the others. The allelopthy of this species was also stronger than others(p<0.05). Taking into account factors such as leaf size, collection and cultivation, Shibataea chinensis Nakai with the advantage of larger leaf, easier picking and wider range of cultivation, was selected as the further research object.(2) The content of secondary metabolites and allelopathy of the different polarity fractions from Shibataea chinensis Nakai leaf were compared. The methanol extract of Shibataea chinensis Nakai leaf was prepared to four different polarity fractions i.e. petroleum ether fraction, ethyl acetate fraction, n-butanol fraction and water fraction. The result showed that ethyl acetate fraction showed the highest total phenolic(32.57 %), total flavonoids(23.38 %) and titerpenoids(15.29 %) content, followed by n-butanol fraction, which of total phenolic(30.73 %), total flavonoids(21.84 %) and titerpenoids(9.13 %). The yield of n-butanol fraction was significant higher than that of ethyl acetate fraction, reache to 4.85 %. Meanwhile, the allelopthy of n-butanol fraction was also stronger than others(p<0.05). The rate to inhibite Lactuca sativa L. seed germination reached 100 % at the concertration of 10 g/L, while reached the same degree for Cucumis sativus L seed at the concentration of 40 g/L.(3) The characteristic compounds of Shibataea chinensis Nakai leaf were isolated, purified and structural analyzed. By using normal phase and reversed-phase silica gel column, RP-C 18, Sephadex LH-20 and thin-layer chromatography, five compounds were isolated from the n-butanol fraction of Shibataea chinensis Nakai leaf extract. They were identified as apigenin, quercetin daucosterol, 5,7-Hydroxy-2-(3,5-Hydroxy-4- methoxyphenyl) Benzopyran-4-one and p-anisic acid. The allelopathy test result showed that all the 5 compounds could inhibit the Lactuca sativa L. and Cucumis sativus L seed germination to a various degree. The allelopathy effect of apigenin, quercetin daucosterol showed concentration-dependent while 5,7-Hydroxy-2-(3,5-Hydroxy-4- methoxyphenyl) Benzopyran-4-one and p-anisic acid showed the phenomenon of “small concentration inhibition, large concentration promotion”.