Caprylic acid in Vitex mollis fruit and its inhibitory activity against a thiabendazole‐resistant Colletotrichum gloeosporioides strain

Abstract

Colletotrichum gloeosporioides causes anthracnose in a large number of crops. Synthetic fungicides are employed to prevent this disease, even though their effectiveness and safety is questionable. Thus, effective and innocuous antifungal compounds are proposed as natural alternatives against anthracnose. The hexane fraction of Vitex mollis pulp (HF-VM) reduces anthracnose incidence in papaya fruit; however, the active compounds and antifungal mechanism of HF-VM are unknown. The aims of this study were to characterize the activity of HF-VM sub-fractions (sHF1 -sHF7 ) against a thiabendazole-resistant Colletotrichum gloeosporioides strain, identify the chemical components and investigate the mechanism of the most active sub-fraction. The sHF3 showed the highest inhibitory activity against Colletotrichum gloeosporioides with a minimal inhibitory concentration (MIC) of 0.5mg mL-1 , whereas thiabendazole (TBZ) had a MIC value higher than 2mg mL-1 . The gas chromatography-mass spectrometry (GC-MS) analysis showed that the compounds in sHF3 were methyl 4-decenoate, caprylic acid, and 24-methylencycloartanol. These compounds are rarely found in fruits and are reported for the first time on Vitex species. The purified 24-methylencycloartanol was inactive (MIC > 0.5mg mL-1 ). In contrast, the commercial standard of caprylic acid presented an elevated activity (MIC=0.125 mg mL-1 ), indicating that this compound is the main one responsible for the antifungal properties of sHF3 . Furthermore, the sHF3 inhibited the spore germination and induced membrane disruption in both the spore and mycelium of Colletotrichum gloeosporioides. Vitex mollis fruit is a novel source of antifungal caprylic acid that could be employed as a marker to prepare standardized extracts with antifungal properties. © 2022 Society of Chemical Industry.