Evaluation of Antifungal Phenolics from Helianthus tuberosus L. Leaves against Phytophthora capsici Leonian by Chemometric Analysis

Phytophthora capsiciLeonian causes destructive economical losses in pepper production, and a promising source of natural fungicides-Helianthus tuberosusleaves was reported. The antifungal activities of different extracts and compounds fromH. tuberosusleaves against the phytopathogen,P. capsiciLeonian, were examined by chemometric analysis, including HPLC-MS/MS and multivariate data analyses. Principal component analysis and orthogonal partial least squares-discriminate analysis were applied to examine the four groups ofH. tuberosusleaves samples, including crude extracts obtained by different methods, including refluxing, macerating, and refluxing under vacuum; four fractions, namely, petroleum ether (PE), chloroform (Chl), ethyl acetate (EA), and n-butanol (NB) fractions; the samples of threeH. tuberosuscultivars; and the samples at three growth stages of cultivar Nan Yu. The phenolics contents were categorized based on 3,5-Dicaffeoylquinic acid (3,5-DiCQA), 1,5-Dicaffeoylquinic acid (1,5-DiCQA), 3-O-Caffeoylquinic acid (3-CQA), and 4,5-Dicaffeoylquinic acid (4,5-DiCQA), which were predominant in all the samples. Antifungal activity assay revealed that Chl and NB fractions were more active againstP. capsiciLeonian with lower IC50(half of maximal inhibitory concentration) values, whereas partial least squares-discriminate analysis suggested caffeoylquinic acid isomer(4-CQA), methyl-quercetin glycoside(MQG), and caffeic acid(CA) might be the main active components inH. tuberosusleaves againstP. capsiciLeonian. Furthermore, microscopic evaluation demonstrated structural deformities inP. capsiciLeonian treated with Chl and NB fractions, indicating the antifungal effects ofH. tuberosusleaves. These results imply thatH. tuberosusleaves with a high concentration of phenolics might be a promising source of natural fungicides.Keywords:Helianthus tuberosus;antifungal activity;phenolic acids;chemometric analysis;PLS-DA