The Inhibitory Effects and Cytotoxic Activities of the Stem Extract of against Single-Stranded DNA-Binding Protein and Oral Carcinoma Cells.

The carnivorous pitcher plants of the genus exhibit many ethnobotanical uses, including treatments of stomachache and fever. In this study, we prepared different extracts from the pitcher, stem, and leaf extracts of obtained using 100% methanol and analyzed their inhibitory effects on recombinant single-stranded DNA-binding protein (SSB) from (KpSSB). SSB is essential for DNA replication and cell survival and thus an attractive target for potential antipathogen chemotherapy. Different extracts prepared from , a tuberous member of the flowering plant family Gesneriaceae, were also used to investigate anti-KpSSB properties. Among these extracts, the stem extract of exhibited the highest anti-KpSSB activity with an IC value of 15.0 ± 1.8 μg/mL. The cytotoxic effects of the stem extract of on the survival and apoptosis of the cancer cell lines Ca9-22 gingival carcinoma, CAL27 oral adenosquamous carcinoma, PC-9 pulmonary adenocarcinoma, B16F10 melanoma, and 4T1 mammary carcinoma cells were also demonstrated and compared. Based on collective data, the cytotoxic activities of the stem extract at a concentration of 20 μg/mL followed the order Ca9-22 > CAL27 > PC9 > 4T1 > B16F10 cells. The stem extract of at a concentration of 40 μg/mL completely inhibited Ca9-22 cell migration and proliferation. In addition, incubation with this extract at a concentration of 20 μg/mL boosted the distribution of the G2 phase from 7.9% to 29.2% in the Ca9-22 cells; in other words, the stem extract might suppress Ca9-22 cell proliferation by inducing G2 cell cycle arrest. Through gas chromatography-mass spectrometry, the 16 most abundant compounds in the stem extract of were tentatively identified. The 10 most abundant compounds in the stem extract of were used for docking analysis, and their docking scores were compared. The binding capacity of these compounds was in the order sitosterol > hexadecanoic acid > oleic acid > plumbagin > 2-ethyl-3-methylnaphtho[2,3-b]thiophene-4,9-dione > methyl α-d-galactopyranoside > 3-methoxycatechol > catechol > pyrogallol > hydroxyhydroquinone; thus, sitosterol might exhibit the greatest inhibitory capacity against KpSSB among the selected compounds. Overall, these results may indicate the pharmacological potential of for further therapeutic applications.