Isolation and antioxidant activity of isoflavone compounds in n-hexane extract of hibiscus manihot l

Hibiscus manihot L leaf contains isoflavone compounds that have the ability to slow down or prevent the oxidation of other molecules. The aim of this study was to isolate and determine the antioxidant capacity of isoflavone compounds contained in n-hexane extract of Hibiscus manihot L leaves associated to its ability as an anti-free radicals (free radical scavenger). Maceration of 1000 g of dry powder of Hibiscus manihot L leaves with 96% ethanol produced as much as 27.43 g viscous extract. Furthermore, the partition with n-hexane produced 4.81 g of blackish brown extract.
The results of antioxidant activity by the method of 1,1-diphenyl-2-pycrylhidrazil (DPPH) showed that n-hexane extract of Hibiscus manihot L leaves yielded IC50 value of 9.68 mg/mL Separation and purification of n-hexane extract were performed by thin layer chromatography and column chromatography resulted in five fractions (FA, FB, FC, FD, and FE).
Phytochemical screening results showed that n-hexane extract contained flavonoids.The characterization of FA isolates by spectrophotometry UV-Vis showed that FA exhibited in two absorption bands which were at λ 329.60 nm (band I) and λ 266.30 nm (band II). It revealed that FA contained flavonoids of isoflavone group in which no free OH groups was found on the A ring and as well as contained ortho-dihydroxy groups on the A ring. The analysis of infrared spectrum showed that FA isolates might contain the functional groups of CH aromatic, CH aliphatic, C=O ketones, C=C aromatic and C-O-C ether. It could be concluded that FA isolates was a flavonoid compound of isoflavone group i.e. 5,7-dihydroxy isoflavone that had strong antioxidant activity against DPPH.