Coleus aromaticus Benth.-A Plant with Strong Anticancer and Antioxidant Potential In Vitro

Background/Objectives: Gastrointestinal cancers, including gastric and colon cancers, constitute a serious threat to global health due to their high incidence and limited treatment outcomes. Thus, natural products are becoming increasingly popular as potential chemopreventive agents. Coleus aromaticus Benth. is mainly used as a tasty addition to dishes and juices due to its aromatic and nutritional properties. The plant has many biological and pharmacological effects that require deeper evaluation. In this study, anticancer, antioxidant, and antimicrobial activities of ethanol, ethanol/water extracts, and juice from C. aromaticus leaves were evaluated. Methods: (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) MTT assay, DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonate)), molybdenum reducing power assay, and broth microdilution technique were used, respectively. Additionally, total phenolic (TPC) and total flavonoid content (TFC) with basic phytochemical composition of volatile compounds by GC-MS and GC-FID were assessed. Results: The results indicate that the strongest anticancer activity was provided by the ethanol extract with IC₅₀ values of 4.94 ± 0.48 and 24.99 ± 1.80 µg/mL on human gastric AGS cells and human colorectal HCT 116 cells, respectively. The antioxidant potential was also the highest for the ethanol extract with IC₅₀ values of 13.34 ± 0.11 (ABTS), 22.90 ± 1.30 (DPPH), and 290.17 ± 4.23 µg/mL (molybdenum reducing power). Antimicrobial experiments revealed that ethanol and ethanol/water extracts were the most potent on Clostridium perfringens (MIC value was <0.02 mg/mL). Phytochemical analysis showed a significant content of phenolic and flavonoid compounds in the ethanol extract (75.87 ± 0.96 mg gallic acid equivalent/g dry extract and 176.01 ± 3.58 mg quercetin equivalent/g dry extract, respectively). Furthermore, all the extracts contained carvacrol (49.09, 28.15, and 25.68% of volatile fraction in ethanol, ethanol/water extracts and juice, respectively). Camphor and oleamide were also detected in large quantity. Conclusions: C. aromaticus can be considered as a potential agent in the prevention and treatment of gastrointestinal cancers, especially the ethanol extract from the plant leaves due to its strong anticancer and antioxidant properties.