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

In the case of obesity, enlarged adipocytes cause an imbalance in lipid metabolism and increased oxidative stress, leading to excessive production of reactive oxygen species (ROS). ROS contribute 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, which simultaneously suppresses lipid accumulation and ROS.

We determined the total flavonoid content of the extracts and identified the functional ingredients by HPLC. Cell viability and proliferation were evaluated in 3T3-L1 cells. The total lipid and triglyceride (TG) contents in 3T3-L1 cells and the nematode Caenorhabditis elegans were measured using Oil Red O staining and TG assay, respectively. A quantitative polymerase chain reaction (qPCR) analysis was performed to investigate the mRNA quantity and accumulated ROS in nematodes.

Apigenin was the major compound in the E. splendens extracts and was most abundant in the flower. The E. splendens flower extract did not show toxicity at concentrations of 25-100 μg/mL and had the highest apigenin content, thus we used the flower extract in the subsequent tests. E. splendens flower extract and apigenin inhibited total lipid and TG accumulation in 3T3-L1 cells and nematodes. These effects were attributed to the inhibition of peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα) expression, which are involved in adipocyte differentiation. In addition, the flower extract and apigenin induced the nuclear localization of DAF-16, which is involved in lipogenesis in nematodes. The flower extract and apigenin also inhibited ROS accumulation in nematodes.

Research on E. splendens has mainly focused on its cultivation and growth. Investigation of the effects of E. splendens on metabolic diseases, including obesity, has been limited and this study provides new insights. Our results suggest that E. splendens flower extract is a valuable material to inhibit lipid and ROS accumulation, and indicate that apigenin-rich functional plant materials should be considered as potential agents against obesity and related diseases.