Genotype diversity and biological activities of toxic arbila ( Phaseolus lunatus L.) from Timor Island

Background and aim Arbila (Phaseolus lunatus L.) is a culturally important legume on Timor Island, where poisonous genotypes are traditionally consumed only after repeated boiling to reduce cyanogenic toxicity. However, the phytochemical composition and biological activities of these poisonous genotypes remain poorly understood. This study aimed to characterize their phytochemical profiles and evaluate their antioxidant, antibacterial, tyrosinase-inhibitory, and cytotoxic activitiesExperimental approach Ethanolic seed extracts from eight poisonous arbila genotypes were subjected to qualitative phytochemical screening and evaluated using DPPH radical scavenging, agar well diffusion, mushroom tyrosinase inhibition, and MTT-based cytotoxicity assays against cancer cell lines (HeLa, MCF-7, HepG2, and SH-SY5Y) and normal human dermal fibroblasts (NHDF).Key findings All genotypes contained alkaloids, tannins, triterpenoids, carbohydrates, and coumarins, whereas flavonoids, steroids, and saponins varied among genotypes. Moderate antioxidant activity was observed, with IC50 values ranging from 117.10 to 155.14 ppm. Selective antibacterial activity was detected only against Cutibacterium acnes, with inhibition zones reaching up to 32 mm. Tyrosinase inhibition was negligible, with approximately 95% enzyme activity retained. Cytotoxicity assays demonstrated genotype-dependent responses. Orange-brown and black-cream arbila exhibited relatively greater cytotoxic activity toward MCF-7 cells, whereas most extracts showed minimal cytotoxicity toward NHDF cells (cell viability >85%). Overall, the cytotoxic findings should be regarded as preliminary evidence of selective bioactivity under the experimental conditions employed.Conclusions Poisonous arbila genotypes exhibit marked chemotypic diversity accompanied by selective biological activities despite their inherent cyanogenic toxicity. These findings indicate that poisonous arbila represents a source of bioactive compounds that warrants further phytochemical characterization, bioactivity-guided fractionation, quantitative cyanogenic analysis, mechanistic investigation, and comprehensive safety evaluation before any potential applications in the food, pharmaceutical, or cosmetic sectors can be considered.