Phytochemical composition of calyx extract of roselle (Hibiscus sabdariffa L.) genotypes
Thirty five roselle genotypes were evaluated at the experimental field of Bangabandhu Sheikh Mujibur Rahman Agricultural University during August 2015 to February 2016. Based on agronomic performance 15 genotypes were selected for the analysis of phytochemical composition and the nutritional quality of calyx extract. The objective of the research was to estimate phytochemical constituents such as carotenoid, flavonoid, phenol, anthocyanin, vitamin C content and antioxidant activity of calyx extract of roselle. The genotype BUM-003 (873.61 μg/g) contained high amount of phenol among the 15 genotypes followed by BUM-007 (867.84 μg/g) and the lowest (481.57 μg/g) in genotype 4561. The high amount of carotenoid was estimated in the genotypes BUM-003, BUM-004, BUM-007 (30.18, 30.95, 29.69 μg/g, respectively). The genotypes 1740 (7.07 μg/g) and 4561 (7.73 μg/g) contained less amount of carotenoid. All the genotypes contained high amount of anthocyanin (>80 μg/g) except 1740, 4561, BUM-002. High amount of flavonoid was estimated in the calyx extract of the genotypes BUM-003 (399.15 μg/g) and BUM-004 (407.34 μg/g). The highest amount of antioxidant was estimated in the genotype BUM-002 (492.87 μg/g) followed by 4385 (488.09 μg/g) and 4920 (487.99 μg/g). Antioxidant activity was determined by 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) radical scavenging assay and maximum was found in the genotype 4920 (95.09%) followed by 4385 (94.12%), BUM-002 (93.55%) and minimum (72.83%) in the genotype 4537. The highest amount of vitamin C was estimated in the genotypes BUM-003 (312.97 μg/g) and the lowest in the genotype 4561 (26.20 μg/g). From the overall phytochemical composition it might be concluded that the calyces of the genotypes 4385, 4920, BUM-002, BUM-003, BUM-004, BUM-007 are the excellent source of natural antioxidants. The calyx extract of the genotype BUM-004 contain the highest amount of carotenoids (31μg/g), ascorbic acid (424.19μg/g), antioxidant (485.85 μg/g BHT eqv) and antioxidant activity (94.50 %). The genotype 4537 contain the highest amount anthocyanins (87.7 μg/g and) and flavonoid (404.40μg/g). The genotype BUM-003 (869.45 μg/g) contained the highest amount of phenol in the calyx extract.
Keywords: Roselle (Hibiscus sabdariffa L.), nutrition, chemical composition, calyx extract