Accumulation and transformation of C6, C9 and C12 phenols from the peel, leaves and branches of Nephelium lappaceum L.

Nephelium lappaceum L. is a tropical fruit with a characteristic hairy appearance, whose peel is used to reduce fever and diarrhea, while its leaves are employed to mitigate headaches. These advantages are mostly attributed to the accumulation of phenolic-related compounds in N. lappaceum. To investigate phenols accumulation and transformation in N. lappaceum peel, leaves and branches, this study investigated the major metabolites and their antioxidant and xanthine oxidase (XO) inhibitory activities. The results showed that the characteristic metabolites in peel, leaves and branches reflected a conversion process from simple phenols (C6) to phenylpropanoids (C9), and then to flavonoids (C12). The peel extract exhibited the highest antioxidant activity, driven by its predominant simple phenols, gallic acid (Ph7). The branch extracts displayed the strongest XO inhibitory activity, primarily attributed to the flavonoids: kaempferol 7-O-α-L-rhamnopyranoside (Fl9), miquelianin (Fl34) and procyanidin B2 (Fl8). This study provides new directions for precisely utilization of N. lappaceum by-products.