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

Abstract

<i>Phytophthora capsici</i> Leonian causes destructive economical losses in pepper production, and a promising source of natural fungicides- <i>Helianthus tuberosus</i> leaves was reported. The antifungal activities of different extracts and compounds from <i>H. tuberosus</i> leaves against the phytopathogen, <i>P. capsici</i> 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 <i>H. tuberosus</i> 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 <i>H. tuberosus</i> 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-<i>O</i>-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 <i>P. capsici</i> Leonian 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 in <i>H. tuberosus</i> leaves against <i>P. capsici</i> Leonian. Furthermore, microscopic evaluation demonstrated structural deformities in <i>P. capsici</i> Leonian treated with Chl and NB fractions, indicating the antifungal effects of <i>H. tuberosus</i> leaves. These results imply that <i>H. tuberosus</i> leaves with a high concentration of phenolics might be a promising source of natural fungicides.