Flavonoid compounds and their antioxidant activity in extract of some tropical plants

The study was counducted to investigate flavonoids content and antioxidant activities in some tropical plants namely cabbage (Brassica oleracea), green chilli (Capsicum annum), red chilli (Capsicum annum), carrot (Daucus carota), red spinach (Amaranthus gangeticus), white radish (Raphanus sativus), lemon grass (Cymbopogon citratus) and turmeric (Curcuma longa). Total flavonoid (TF) content was observed to be highest in red chili (0.939 mg/g DW) and low content of TF was observed in red spinach (0.066 mg/g DW). High performance liquid chromatography (HPLC) was employed to identify and quantify the five important flavonoid components (quercetin, catechin, kaempferol, apigenin and rutin). High content of quercetin (0.639 mg/g DW), catechin (0.14 mg/g DW), apigenin (0.047 mg/g DW) and rutin (0.069 mg/g DW) was detected from red chilli and high content of kaempferol (0.13 mg/g DW) was detected from carrot. Red chilli with high flavonoid compounds showed highest antioxidant activity (78.66%) determined by the 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) assay. Results suggested a good potential of flavonoid compounds and antioxidant activity in red chilli and this plant could be useful for both food flavourings and in traditional medicine.   Key words: Total flavonoid, high performance liquid chromatography (HPLC), red chilli, antioxidant activity.