Chasing the ‘unusual suspects’ underlying the procarcinogenic effects of Areca catechu nut

Resumo

Background: The high incidence of oral cancers in Asian countries is strongly linked to Areca nut mastication (Areca catechu L.). While areca alkaloids are recognized for their psychoactive effects, the precise cancer-inducing constituents remain unclear. Arecoline is often labeled as the main culprit, but the chemical complexity of A. catechu suggests the involvement of other compounds in carcinogenesis [1]. Objective: This study aims to further characterize the constituents in A. catechu that may contribute to carcinogenesis. Methods: Effects on matrix metalloproteinases were assessed through enzymatic assays (up to 200 µM), same applying to the impact on the activity of lipoxygenase 5 (LOX-5) and acetylcholinesterase. Effects on the cell viability of buccal mucosa cells were assessed in TR-146 cells via the MTT and NR assays, after exposure to the aqueous extract of A. catechu or its isolated phytochemicals (up to 1 mg/mL or 800 µM, respectively). Results: Significant inhibition of 5-LOX activity was observed, particularly with (+)-catechin and (-)-epicatechin (58% and 72%, respectively, p < 0.001) at 200 µM. Guvacoline and isoguvacine (28% and 35%, respectively, p < 0.01) also exhibited inhibition at concentrations higher than 100 µM. Guvacoline and isoguvacine significantly inhibited acetylcholinesterase (38%, p < 0.05), suggesting modulation of cholinergic neurotransmission, arecoline exhibiting the most potent effect (62%, p < 0.001) reinforcing its neuroactive role. Arecoline significantly reduced the viability of buccal mucosa cells at ≥400 µM (p < 0.001), with a marked reduction at 800 µM. Gallic and gallotannic acid exhibited cytotoxicity only at 800 µM (p < 0.001 and p < 0.01, respectively). A. catechu extract demonstrated high toxicity at 1 mg/mL (p < 0.01), suggesting a possible synergistic effect of its components. Conclusions: Flavonoids strongly inhibit 5-LOX, while alkaloids affect acetylcholinesterase and cause significant toxic effects upon TR-146 cells both at mitochondrial and lysosomal levels.