Evaluation of Antifungal Phenolics from L. Leaves against Leonian by Chemometric Analysis.

Leonian causes destructive economical losses in pepper production, and a promising source of natural fungicides- leaves was reported. The antifungal activities of different extracts and compounds from leaves against the phytopathogen, Leonian, 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 of leaves 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 three cultivars; 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--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 against Leonian with lower IC(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 in leaves against Leonian. Furthermore, microscopic evaluation demonstrated structural deformities in Leonian treated with Chl and NB fractions, indicating the antifungal effects of leaves. These results imply that leaves with a high concentration of phenolics might be a promising source of natural fungicides.