Sechium edule (Jacq.) Swartz, a New Cultivar with Antiproliferative Potential in a Human Cervical Cancer HeLa Cell Line

Abstract

The Sechium edule Perla Negra cultivar is a recently-obtained biological material whose progenitors are S. edule var. nigrum minor and S. edule var. amarus silvestrys, the latter of which has been reported to have antiproliferative activity against the HeLa P-388 and L-929 cancer cell lines. The present study aimed to determine if the methanolic extract of the fruit of the Perla Negra cultivar had the same biological activity. The methanolic extract was phytochemically characterized by thin layer chromatography (TLC) and column chromatography (CC), identifying the terpenes and flavonoids. The compounds identified via high performance liquid chromatography (HPLC) were Cucurbitacins B, D, E, and I for the terpene fractions, and Rutin, Phlorizidin, Myricetin, Quercetin, Naringenin, Phloretin, Apigenin, and Galangin for the flavonoid fractions). Biological activity was evaluated with different concentrations of the methanolic extract in the HeLa cell line and normal lymphocytes. The methanolic extract inhibited the proliferation of HeLa cells (IC₅₀ 1.85 µg·mL^-1), but the lymphocytes were affected by the extract (IC₅₀ 30.04 µg·mL^-1). Some fractions, and the pool of all of them, showed inhibition higher than 80% at a concentration of 2.11 µg·mL^-1. Therefore, the biological effect shown by the methanolic extract of the Perla Negra has some specificity in inhibiting tumor cells and not normal cells; an unusual feature among molecules investigated as potential biomedical agents.

Keywords: Perla Negra; biological activity; cancer; chayote.

Figure 1

Proliferation assay. (A) Inhibitory effect of amarus silvestrys on HeLa cells; (B) HeLa cells and lymphocytes with the Perla Negra methanolic extract at different concentrations (0 µg·mL⁻¹, 1.25 µg·mL⁻¹, 1.56 µg·mL⁻¹, 1.85 µg·mL⁻¹, 2.5 µg·mL⁻¹, and 5 µg·mL⁻¹) and Cisplatin (0.72 µg·mL⁻¹) for 72 h. Different letters indicate statistical significances 1A (a, b, c, and d) 1B (a, b, and c) (p ≤ 0.001).

Figure 1

Proliferation assay. (A) Inhibitory effect of amarus silvestrys on HeLa cells; (B) HeLa cells and lymphocytes with the Perla Negra methanolic extract at different concentrations (0 µg·mL⁻¹, 1.25 µg·mL⁻¹, 1.56 µg·mL⁻¹, 1.85 µg·mL⁻¹, 2.5 µg·mL⁻¹, and 5 µg·mL⁻¹) and Cisplatin (0.72 µg·mL⁻¹) for 72 h. Different letters indicate statistical significances 1A (a, b, c, and d) 1B (a, b, and c) (p ≤ 0.001).

Figure 2

Proliferation assay. The effect of the Perla Negra cultivar fractions on the HeLa cell line. The polarity of fractions is related to the mobile phase of the TLC in the tracking of the terpene compounds. The cells were incubated with all fractions, the methanolic extract, and the pool at the same concentration (2.11 µg·mL⁻¹) and Cisplatin (0.72 µg·mL⁻¹) for 72 h. Different letters indicate statistical significances (a, b, c, d, e, and f) (p ≤ 0.001).

Figure 3

Identifying compounds by HPLC. Chromatograms of the terpenes (cucurbitacins) that showed biological activity, which were obtained from the methanol extract of Perla Negra through column chromatography, where the presence of cucurbitacins and other non-identified compounds is confirmed at 235 nm.

Figure 3

Identifying compounds by HPLC. Chromatograms of the terpenes (cucurbitacins) that showed biological activity, which were obtained from the methanol extract of Perla Negra through column chromatography, where the presence of cucurbitacins and other non-identified compounds is confirmed at 235 nm.

Figure 4

Identifying compounds by HPLC. (A) Chromatograms of the flavonoid fractions that showed biological activity, obtained from the methanolic extract of Perla Negra through column chromatography at 254 nm; and (B) the presence of Apigenin at 316 nm and unidentified compounds.