Phenolic extracts from wild edible plants to control postharvest diseases of sweet cherry fruit

Postharvest treatments with extracts from two wild edible plants (Orobanche crenata and Sanguisorba minor), water solutions of two inorganic salts (calcium chloride, CaCl2, and sodium bicarbonate, NaHCO3), and their combination (i.e., extracts with added CaCl2 or NaHCO3), were assayed to control sweet cherry postharvest diseases. Three extract concentrations for each plant were assayed, corresponding to 0.170, 0.340, and 0.510 g dry matter/mL and to 0.125, 0.250, and 0.500 g dry matter/mL for S. minor and O. crenata, respectively. At the lowest and the highest concentrations tested, S. minor extract was able to inhibit rot development in stored fruit by 79 and 89%, respectively, with an efficacy comparable to that of CaCl2 and NaHCO3; for O. crenata extract such inhibition ranged between 64 and 76%, respectively. A dose effect was observed only for O. crenata. Moreover, the level of control was not improved by the combined application of plant extracts and salts. HPLC analysis of O. crenata extract showed verbascoside as the main phenolic compound, being about 95% of total phenolics; S. minor phenolic pattern appeared to be more complex, due to the presence of caffeic acid derivatives, quercetin-3-glucoside, kaempferol-3-glucoside and other quercetin, kaempferol, and luteolin derivatives, as well as many other unidentified compounds. Residues of phenolics resulting from plant extracts in treated sweet cherries after storage were below the analytical limit of detection. The study demonstrated that S. minor and O. crenata extracts might represent an alternative organic mean for controlling sweet cherry postharvest decay.