Polyphenolic HRMS Characterization, Contents, Antioxidant Activity and Cytotoxic Effects of Costa Rican Ocimum tenuiflorum L. Extracts

Holy basil (Ocimum tenuiflorum) is well known for its bioactive properties, including antioxidant and anti-inflammatory effects. Leaves samples from Costa Rica were extracted and analyzed in composition and in antioxidant and cytotoxic activities. The analysis by Ultra Performance Liquid Chromatography coupled with High Resolution Mass Spectrometry using a quadrupole-time-of-flight analyzer (UPLC-QTOF) allowed the identification of 12 compounds, including 7 glycosylated flavonoids, 2 coumaroyl alcohols, rosmarinic acid, eugenol, and salvianolic acid E. Quantification using liquid chromatography with diode array detector (UPLC-DAD) was performed for the main components, including apigenin and luteolin glucoronides, rosmarinic acid, and eugenol, revealing an overall content of 78.28–121.05 mg/g dry extract. Total phenolic values ranged between 74.5 and 122.5 mg GAE/g dry extract, while antioxidant evaluations showed IC50 values of 28.18–48.18 mg dry extract/L for 2,2-diphenyl-1-picrylhidrazyl (DPPH) assay, 1192.8–2006.5 μmol Trolox/g dry extract for Ferric Reducing Antioxidant Power (FRAP), 2.56–3.01 μmol Trolox/mg dry extract for Oxygen Radical Absorbance Capacity (ORAC), and 708.7–1415.8 μmol Trolox/g dry extract for Trolox Equivalent Antioxidant Capacity (TEAC). Pearson correlation analyses (p < 0.05) between the quantified phenolic content and the antioxidant assays showed the highest values between UPLC and DPPH (R = 0.962) and UPLC with ORAC values (R = 0.955). A Relative Antioxidant Capacity Index (RACI) evaluation indicated HB-1 and HB-3 samples as the ones with the best results in these antioxidant assays, aligning with their higher content in polyphenols, which can be attributed to their higher maturity at the harvesting stage in comparison with HB-2. The in vitro cytotoxicity evaluation of these extracts in adenocarcinoma cell lines, using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, showed a significant cytotoxic effect against AGS gastric cancer cell lines with an IC50 of 78–150 μg extract/mL and a selectivity index greater than 6 in respect to normal Vero cell lines. To the best of our knowledge, this work represents the first study of its kind in O. tenuiflorum from Costa Rica.