Effect of Apigenin-Enriched Elsholtzia splendens Flower Extract on Lipid and Reactive Oxygen Species (ROS) Accumulation in 3T3-L1 Cells and Caenorhabditis elegans

Research background. In the case of obesity, enlarged adipocytes cause lipid metabolism imbalance and increased oxidative stress, leading to excessive reactive oxygen species (ROS) production. ROS contributes to metabolic disorders such as inflammation and insulin resistance, further worsening lipid imbalance and promoting obesity-related diseases. Therefore, we investigated the benefits of Elsholtzia splendens that simultaneously suppresses lipid accumulation and ROS. Experimental approach. We determined the total flavonoid content of the extracts and analysed them by HPLC to identify the functional ingredients. Cell viability and proliferation were evaluated in 3T3-L1 cells. The total lipid and triglyceride (TG) contents of cells and nematodes were measured by Oil Red O and TG assay, respectively. A qPCR analysis was performed to investigate the mRNA and accumulated ROS in nematodes. Results and conclusions. Apigenin was the major substance in the E. splendens extracts and was most abundant in the flower part. The E. splendens flower extract (ESFE) did not show toxicity at concentrations of 25–100 μg/mL and had the highest apigenin content, thus we used ESFE in the subsequent test. ESFE and apigenin inhibited total lipid and TG accumulation in 3T3-L1 cells and nematodes. These effects were attributed to the inhibition of PPARγ and C/EBPα expression, factors involved in adipocyte differentiation. In addition, ESFE and apigenin induced the nuclear localization of DAF-16, which is involved in lipogenesis in nematodes. Also, ESFE and apigenin inhibited ROS accumulation in nematodes. Novelty and scientific contribution. Research on E. splendens has mainly focused on its cultivation and growth. Research on the effects of E. splendens on metabolic diseases, including obesity, has been limited and this study provides new insights. Our results imply that ESFE is a valuable material to inhibit lipid and ROS accumulation, and suggest that apigenin-rich functional plant materials should be considered as potential agents against obesity and related diseases.