Antioxidant and selective cytotoxic activity of Dipterocarpus obtusifolius flower extract against gastrointestinal cancer, with bioactive component profiling

Abstract

Background: Gastrointestinal (GI) malignancies exhibit significant global variations in incidence and mortality. Late diagnosis remains a major challenge especially gastric and cholangiocarcinoma, particularly in Thailand. Novel therapeutic agents from our region’s traditional medicinal plants are crucial for developing cancer treatments. Dipterocarpus obtusifolius Teijsm. ex Miq., widely used in Southeast Asian traditional medicine. This study aims to bridge this gap by evaluating the phytochemical composition, antioxidant activity, cytotoxicity, and pro-apoptotic effects of crude ethanol and ethyl acetate extracts of this flower on human gastric cancer (AGS) and cholangiocarcinoma (KKU-100) cell lines. Methods: Antioxidant activity was determined using FRAP and DPPH assays, complemented by measurements of total phenolic and flavonoid contents via Folin-Ciocalteu and aluminum chloride colorimetric assays. For anticancer effects, we assessed cytotoxicity and pro-apoptotic effects in KKU-100 and AGS cell lines, further investigating downstream apoptosis by quantifying Bax and caspase-3 mRNA expression using real-time RT-PCR. Phytochemical profiling was also conducted via GC-MS and NMR. Results: Flowers extraction of Dipterocarpus obtusifolius Teijsm. ex Miq. showed stronger FRAP activity was seen in the ethyl acetate extract, corresponding to its higher phenolic content, while greater DPPH scavenging activity (EC<inf>50</inf> = 0.8681 mg/mL) and higher flavonoid content demonstrated in ethanol extract. Notably, the ethanol extract exhibited the strongest cytotoxic activity against KKU-100 cells, with an IC<inf>50</inf> of 74.46 µg/mL after 48 h and 45.72 µg/mL after 72 h, while the strongest cytotoxic activity against AGS cells exhibited in the ethyl acetate, with an IC<inf>50</inf> of 113.7 µg/mL after 48 h and 66.41 µg/ml after 72 h. A concentration-dependent induction of apoptosis and a significant G1 phase cell cycle arrest was found in both cell lines via upregulation of Bax and Caspase-3 expression, both key regulators in apoptotic pathways. The phytochemical composition of these extracts using GC-MS analysis revealed distinct profiles. The ethanol extract was rich in decylaldehyde and 6,7-dimethoxycoumarin, while the ethyl acetate extracts predominantly contained copaene, gurjunene, and caryophyllene. Similar patterns were observed in 1 H NMR analysis of both extraction, which reveals that the metabolites present in the highest concentration are leucine, lignin and elaidic acid. Notably, many of these identified compounds have prior associations with antioxidant and apoptosis-inducing activities. Conclusion: This study provides the first in vitro evidence that the Dipterocarpus obtusifolius Teijsm. ex Miq. flower extract possesses significant antioxidant activity and potent anti-proliferative effects against both cholangiocarcinoma and gastric adenocarcinoma cell lines.