Citrus Polymethoxylated Flavones Can Confer Resistance against <i>Phytophthora citrophthora</i>, <i>Penicillium digitatum</i>, and <i>Geotrichum</i> Species

Abstract

The polymethoxylated flavones observed in the essential oils of the byproducts of various Citrus fruits after industrial processing were as follows: sinensetin, nobiletin, and heptamethoxyflavone in clementine; sinensetin, quercetogetin, nobiletin, heptamethoxyflavone, and tangeretin in sour orange and sweet orange. Penicillium digitatum was totally inhibited (100%) by application of the polymethoxylated flavones present in the extracts from the clementine and sweet orange oils and 77% inhibited by those extracted from the sour orange oil. Phytophthora citrophthora was 100% inhibited by sour orange oil, 72% by clementine oil, and only 14% by sweet orange oil. Geotrichum sp. was more sensitive to the sour orange extract, being inhibited by ∼57%, whereas clementine and sweet orange produced inhibition rates of 47 and 34%, respectively. Keywords: Clementine; heptamethoxyflavone; nobiletin; quercetogetin; sinensetin; sour orange; sweet orange; tangeretin