Antioxidant Activity and Total Phenolic Content of Underutilized Edible Tree Species of the Philippines

Recently, neglected and underutilized species (NUS) have deservedly come to the forefront of scientific interest because they can contribute to the human nutrition, due to the content of bioactive substances such as antioxidants. Despite the great diversity and rich tradition in the use of Philippine NUS, the nutritional properties of many edible plants remain unexplored. The main objective of this study was to evaluate various parts of eleven NUS fruits and vegetables traditionally consumed in the Philippines, namely Allaeanthus luzonicus, Canarium ovatum, Dillenia philippinensis, Ficus pseudopalma, Flacourtia indica, Flacourtia inermis, Garcinia intermedia, Heliotropium arboreum, Posoqueria latifolia, Stelechocarpus burahol, and Sterculia quadrifida for their total phenolic content (TPC) and in vitro antioxidant activity (DPPH and ORAC assays). Inflorescence of A. luzonicus (DPPH IC50 = 91.0 μg/mL, ORAC IC50 = 37.9 μg/mL) and fruit of S. burahol (DPPH IC50 = 253.7 μg/mL, ORAC IC50 = 32.2 μg/mL) showed the strongest antioxidant activity in both assays. These two species also had the highest TPC (202.1 and 133.0 µg GAE/mg extract, respectively). For all samples tested, a strong correlation was found between TPC and antioxidant activity. Based on our results, A. luzonicus and S. burahol have promising potential as novel antioxidant rich food.