Anti-obesity Activity of Chlorophyll a from Spirulina (Arthrospira platensis) Through the Inhibition of Pancreatic Lipase Enzyme

Obesity is considered a metabolic disease and a risk factor for other diseases. Spirulina (Arthrospira platensis) a blue-green microalgae belonging to the cyanobacterium group is rich in chlorophyll a. Spirulina extract has been shown to have pancreatic lipase inhibitory activity. This study aimed to determine the anti-obesity activity of diethyl ether fraction and chlorophyll a from Spirulina extract.  Spirulina was extracted by maceration in methanol:acetone (7:3). The pigments including chlorophyll were separated from the extract by fractionation with diethyl ether. Chlorophyll a was isolated from the diethyl ether fraction by preparative thin layer chromatography (Prep-TLC). Chlorophyll a was identified by ultra violet-visible (UV-Vis), and fourier transform infra-red (FTIR) spectrophotometry. The anti-obesity activity of both the diethyl ether fraction, and chlorophyll a was evaluated by pancreatic lipase inhibition assay in vitro. The anti-obesity activity of chlorophyll a was further assessed in silico by molecular docking with human monoacylglycerol lipase enzyme (PDB ID: 5ZUN). Drug-likeness, and ADMET properties of chlorophyll a were also predicted. Results showed that, both the diethyl ether fraction, and chlorophyll a from Spirulina extract exhibited anti-obesity activity with IC50 values of 167.16 ± 1.08 µg/mL, and 23.47 ± 0.83 µg/mL, respectively. The anti-obesity activity of chlorophyll a was comparable to that of the positive control (orlistat) with IC50 of 20.53 ± 1.97 µg/mL.  Chlorophyll a also exhibited potent anti-obesity activity in silico, with a binding affinity of -11.66 kcal/mol to 5ZUN protein. However, chlorophyll a did not meet the drug-likeness criteria, and was predicted to hepatotoxic and cardiotoxic.