Optimization of explant type and auxin-cytokinin combinations for enhanced organogenesis, solasodine accumulation, and cytotoxicity in Solanum trilobatum L.

Solanum trilobatum L. is a medicinal climber valued for its steroidal alkaloids, particularly solasodine, but its natural propagation is limited. This study established a high-frequency regeneration protocol by comparing shoot tip, node, petiole, and leaf explants on MS medium with various auxin-cytokinin combinations. Leaf explants on 0.1 mg/L IAA + 2.5 mg/L Kin produced the highest shoots (32/explant). Friable callus induced on 2 mg/L 2,4-D was used to establish suspension cultures (PCV 0.756 mL/mL). Biochemical analysis revealed maximum carbohydrates in in vitro shoots (10.623 mg/g FW) and peak proteins in flowering in vivo shoots (12.654 mg/g FW). Phytochemical analysis showed that control and in vitro shoots contained seven steroid fractions including solasodine (1.107 and 1.007 mg/g respectively), which was absent in in vivo shoots. Cytotoxicity assays against DLA cells demonstrated that total steroid fractions from in vitro shoots caused 100% cell death at 80 µg, with CC₅₀ values of 22.5 µg (diosgenin) and 21.0 µg (betulin). Hardened plantlets achieved 80% field survival. The loss of solasodine during acclimatization suggests that direct harvesting of in vitro shoots is preferable for steroidal alkaloid production, and the cytotoxic equivalence validates micropropagation for producing therapeutically potent biomass.