Histochemical Localization and Cytotoxic Potential of Alkaloids in Phaedranassa lehmannii

Plants of the subfamily Amaryllidoideae are a source of unique and bioactive alkaloids called Amaryllidaceae alkaloids. The study of their anticancer potential has intensified in recent years. This work aims to locate and characterize the profile of cytotoxic alkaloids biosynthesized and stored in different tissues of Phaedranassa lehmannii Regel using different histochemical methods and chromatographic analysis. The histochemical analysis in the bulbs revealed the presence of alkaloids at the basal edge of the scale-like leaves and bud apical zone. The GC-MS analysis indicated that the bulbs biosynthesize crinane- (9.80 µg/g DW), galanthamine- (8.04 µg/g DW), lycorine- (7.38 µg/g DW), and narciclasine-type (3.75 µg/g DW) alkaloids. The root biosynthesizes alkaloids that are mainly distributed mostly in lycorine- (225.29 µg/g DW) and galanthamine-type (72.35 µg/g DW) alkaloids. The total alkaloids biosynthesized by the root (324.93 µg/g DW) exceeded eleven times the abundance of the alkaloids identified in the bulbs (28.97 µg/g DW). In addition, the total alkaloid fractions exhibited a dose-dependent cytotoxic effect in the evaluated concentrations, with IC₅₀ values of 11.76 ± 0.99 µg/mL and 2.59 ± 0.56 µg/mL against human lung (A549) cancer cells and 8.00 ± 1.35 µg/mL and 18.74 ± 1.99 µg/mL against gastric (AGS) cancer cells. The present study provided evidence to locate and characterize the alkaloids of P. lehmannii grown under nursery conditions as a species producing potential antiproliferative alkaloids.