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Choonospora minima (Hering 1841) is a brown alga belonging to the family Scytosiphonaceae. Natural bioactive compounds are abundant in C. minima with potential active ingredients in the treatment of diabetes. Therefore, the present study aimed to isolate the anti-diabetic compound of the chloroform fraction of methanol extract using bioassay-guided fractionation. De-polysaccharide methanol extract of C. minima was partitioned with increasing solvents; n-hexane, chloroform, ethyl acetate, and fractions were evaluated for their hypoglycemic activity. The chloroform fraction exhibiting potent α-amylase (IC₅₀: 3.17±0.02 μg/ml; IC_{50standard acarbose}: 87.43±0.59 μg/ml) and α-glucosidase (IC₅₀: 1.99±0.01 μg/ml; IC_{50standard acarbose}: 0.38±0.06 μg/ml) inhibitory activities was subjected to sub-fractionation with silica column chromatography (F_A, F_B, F_C, F_D) based on the spots on TLC. The fraction with higher hypoglycemic activity was identified by activity guided fractionation. As fraction “F_C” fraction exhibited potent activity (IC_{50 α amylase}: 93.43±0.45 μg/ml; IC_{50 α glucosidase}: 47.25±0.46 μg/ml), it has further purified using Sephadex-LH20 column chromatography. Based on the TLC spots, eight fractions (F₁, F₂, F₃, F₄, F₅, F₆, F₇ andF₈) were collected and confirmed the hypoglycemic activity through activity guided fractionation. According to the results, fraction F₃ exhibited strong hypoglycemic activity against α amylase (IC_50:88.94±0.44 μg/ml) and α glucosidase IC_50::44.93±0.31 μg/ml)enzyme inhibitory assays. Hence, F₃subtraction was selected to isolate the anti-diabetic active compound through High Performance Liquid Chromatography, and structural elucidation using NMR spectroscopy. Based on the results, a compound belonged to the carotenoids has been isolated from fraction F₃ (compound 1) and confirmation of bioactivity of that particular compound is in progress.

Raymond Andersen

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