The effect of maturity on carotenoids of Lasia spinosa stem and the effects of cooking on in-vitro bioaccessibility of carotenoids

Abstract

In a continuing search for pro-vitamin A carotenoids, Lana spinosa (Linn.) stein (Sinhala: kobila aLa) was examined for the first time. Specimens purchased from the market showed a wide variation in carotenioid content (0.4 -1.8 μg.g-1 fresh weight (FW and 0.9-7.2 μg.g-1 FW for α-carotene and β-carotene respectively) and retinol activity equivalent (RAE, 9.2-67.5 100g-1 FW). Percentage contribution to recommended daily allowance (RDA) of pre-school children by a 25 g portion of Kobia stem ranged from 1.1 to 8.4. Sampling from a home garden showed that there were two distinct leaf types (sagittate (A) and pinnatifid (B)) and a third plant a hybrid type (C). Sampling from the foliage end to terminal root end gave an index of maturity. Carotenoids were separated by Open Column Chromatography (0CC) and identified by chromatographic behavior, UV/Vis spectrophotometrically and chemical tests. The following were identified; α-carotene, β-carotene, β-carotene 5,6,5',6'diepoxide, 5,6,5',6'-diepoxy-5,8,5', 8'-tetrahydro-ββcarotene 3,3'-diol, as-neoxanthin and unidentified carotenoids I, H, III and IV. There was a 14 and 2.3 fold higher content of pro-vitamin A carotenoids in the edible part of the most mature stems of type A and B respectively compared to the most immature stems. Total pro- vitamin A carotenoid content of the most mature part of the stems were 261.4 and 234.6 μg.lOOg-1 FW (RAE was 19.5 and 15.7 100g-1 FW) for type A and B respectively. In-vitro bioaccessibility showed that preparation of curry with coconut milk releases α-carotene and β-carotene in the amounts of 1.1±0.41 μg.g-1 (15.1%) {(Dry weight (DW)) and 5.8±2.1 μg.g-1 (18.3%) DW respectively. On frying, the values were 0.4±0.11 μg.g-1 (10.8%) DW and 1.6±0.48 μg.g-1 (12.1%) DW for α-carotene and β-carotene respectively as determined by high performance liquid chromatography (HPLC). Frying and making curry are the two traditional methods of cooking this vegetable in Sri Lanka.