Ascorbic acid (AA) and dehydroascorbic acid (DHA) are reduced and oxidized forms of vitamin C, which
are ubiquitously found in various fruits and vegetables. The present study has evaluated and optimized
various factors responsible for AA and DHA stability in grapefruit samples. Furthermore, the optimized
method was used to quantify these compounds in different fruits and vegetables. The AA stability in the
samples was evaluated by extracting grapefruit juice using 1, 3 and 5 g/100 mL metaphosphoric acid
(MPA) and trichloro acetic acid (TCA). The AA levels were stable in grapefruit samples extracted with 1, 3
and 5 g/100 mL MPA, whereas TCA extracts showed degradation in 48 h. Among the three reducing
agents studied, tris(2-carboxy ethyl) phosphine hydrochloride (TCEP) has efficiently converted DHA at all
concentrations and the samples were stable for 48 h at 2.5 mmol/L TCEP. Lower pH favored complete
conversion of DHA by TCEP than dithiothreitol. Among various fruits and vegetables analyzed, the
highest levels of AA (260.1 mg/100 g) were observed in guava and DHA (58.6 mg/100 g) in parsley
samples. The current optimized method prevents the degradation of AA and DHA from fruit and vege-
table samples stored at room temperature for two days.