Bioactivity-Directed Isolation of Anticancer Constituents from Underexplored Folklore: Rhus punjabensis Stewart

Medicinal plants continue to offer a promising source of novel bioactive compounds for cancer therapy due to their affordability, biocompatibility, and low toxicity. Rhus punjabensis Stewart, an ethnomedicinal species from the family Anacardiaceae, has long been used in the traditional medicine of northern Pakistan to treat inflammatory, hepatic, and infectious diseases. However, its phytochemical composition and anticancer potential remain largely unexplored.

This study employed a bioactivity-guided isolation strategy to identify and characterize anticancer constituents from R. punjabensis leaves. The plant material was sequentially fractionated using solvents of increasing polarity, followed by purification via column chromatography. Each fraction and purified compound was evaluated using antioxidant (DPPH, total antioxidant capacity, and total reducing power) and cytotoxic assays, including brine shrimp lethality, Sulfo-rhodamine B (SRB) against five human cancer cell lines, protein kinase inhibition, and NF-κB chemo-preventive assays.

Comparative analysis of spectral data (UV, 1D/2D NMR, and ESI-MS) led to the identification of three triterpenoid compounds-Lupeol, Cycloartenol, and β-sitosterol-reported for the first time from R. punjabensis. Among them, Lupeol displayed the most potent cytotoxicity against DU-145 prostate (IC₅₀ = 11.2 ± 1.2 μg/mL) and HL-60 leukemia (IC₅₀ = 15.2 ± 1.1 μg/mL) cell lines and showed significant NF-κB inhibitory activity (IC₅₀ = 19.4 ± 1.1 μg/mL), indicating its chemo-preventive potential. Cycloartenoland β-sitosterol exhibited moderate antioxidant and antimicrobial activities.

The findings validate the ethnopharmacological use of R. punjabensis and confirm it as a new source of triterpenoids with notable anticancer activity. This study provides the first comprehensive account of its bioactive metabolites, reinforcing the significance of bioactivity-directed isolation as a powerful approach for discovering natural anticancer agents. Further in vivo and mechanistic evaluations are warranted to establish their therapeutic efficacy and safety profiles.