Papaya Seed Extract and Recovery of Some Main Constituents

Carica papaya Linn. is one of the most common plants in almost all tropical countries. Its fruit is widely used as food or an ointment in traditional medicine. It is one of the few tropical fruits to contain glucotropaeolin (benzyl glucosinolate) detected in great quantity, mainly in the seeds of papaya. When cells in plant tissue are damaged, glucotropaeolin is hydrolysed by the enzyme myrosinase to benzyl isothiocyanate. The anticancer activity of this latter compound has been widely evidenced, but the metabolic profile of the papaya seed extracts is not reported in the literature. The objective of this study is to investigate the seed extracts of C. papaya L. by UHPLC-PDA ESI/MS, with and without the inactivation of myrosinase, and compare the recovery of some main components using two different inactivation procedures. The extracts (methanol/water, 60:40, v/v) were studied in negative and positive ionisation modes. Separations were carried out on an Acquity BEH C18 (50 × 2.1 mm i.d.) 1.7 μm analytical column, and 0.02% formic acid in water and acetonitrile was used as the mobile phase at a flow rate of 0.6 mL min−1. Beyond the amino acids and glucotropaeolin already detected in papaya seeds, 4-hydroxybenzoic acid, which has never been detected in papaya seeds with this technique before, was identified. Moreover, mono-, di- and tri-glycosides of 4-hydroxybenzoic acid were putatively assigned. Glucotropaeolin, 4-hydroxybenzoic and tryptophan were quantified in seeds extracted after myrosinase deactivation. These three components were more effectively recovered using an oven than microwave myrosinase inactivation.