Bioassay-guided purification of swartzchromone, a novel chromone, as an α-glucosidase inhibitor from Sargassum swartzii C. Agardh (Sargassaceae, brown seaweed)

An undescribed α-glucosidase inhibitor chromone; swartzchromone (1) was isolated from Sargassum swartzii C. Agardh, a brown alga collected from Bushehr coastal area in a bioassy-guided purification procedure. After several purification steps, including liquid-liquid extraction, gel filtration column chromatography, and semi-preparative HPLC, four compounds were obtained, including compound 1, which has a novel carbon skeleton: 6, 7, 8, 9a-tetrahydroxy-3-methoxy-3a, 9a-dihydrocyclopenta[b]chromene-1, 9-dione. Characterisation of the compound was accomplished by ESIMS, UV and 1D and 2D NMR spectral analyses. Interestingly, compound 1 showed a lower IC50 (0.25 ± 0.02 mM) than the standard drug, acarbose. Furthermore, molecular docking analysis and MD simulation suggested 1 as a potent compound with effective interactions with the enzyme’s active sites residues. For the first time, a biogenesis pathway for the chromone compound has also been predicted. Therefore, we propose the algal extract or its purified compounds to be tested in vivo for their potential as antidiabetic natural medicine.