Identification and structural elucidation of bioactive compounds from Scirpoides holoschoenus

Phytochemical investigations of dichloromethane and methanol extracts of roots and rhizomes of Scirpoides holoschoenus afforded 21 stilbenes, six flavonoids, six ferulic acid derivatives and four diterpenes. Among these constituents, six stilbenes, one flavonoid, one diterpene and two ferulic acid derivatives, represent previously unreported natural products. Structure elucidation was performed by HRESI-MS, NMR, GC-MS, and ECD data evaluation. The monoprenylated flavonoid (sophoraflavanone B) and all isolated stilbene oligomers (trans-scirpusin B, scirpusin A, cassigarol E, cyperusphenol B, cyperusphenol D, passiflorinol A, cyperusphenol A and mesocyperusphenol A) showed strong inhibitory activities on spore germination of two Botrytis cinerea strains isolated from field-infected grape berries and apple fruits compared to the reference controls resveratrol, piceid, and fenhexamid at a test concentration of 2.0 mM. For sophoraflavanone B and cyperusphenol A, the EC₅₀ values were determined by concentration response curves and resulted in values of 0.35 mM and 0.53 mM, respectively. The data suggest that stilbene oligomers but also prenylated flavonoids should be examined further to gain more information on their antimicrobial activity and might be a suitable addition to chemical fungicides on the market to combat gray mold.