Bioprospecting of Natural Compounds from Brazilian Cerrado Biome Plants in Human Cervical Cancer Cell Lines

Abstract

Cervical cancer is the third most common in Brazilian women. The chemotherapy used for the treatment of this disease can cause many side effects; then, to overcome this problem, new treatment options are necessary. Natural compounds represent one of the most promising sources for the development of new drugs. In this study, 13 different species of 6 families from the Brazilian Cerrado vegetation biome were screened against human cervical cancer cell lines (CCC). Some of these species were also evaluated in one normal keratinocyte cell line (HaCaT). The effect of crude extracts on cell viability was evaluated by a colorimetric method (MTS assay). Extracts from Annona crassiflora, Miconia albicans, Miconia chamissois, Stryphnodendron adstringens, Tapirira guianensis, Xylopia aromatica, and Achyrocline alata showed half-maximal inhibitory concentration (IC₅₀) values < 30 μg/mL for at least one CCC. A. crassiflora and S. adstringens extracts were selective for CCC. Mass spectrometry (Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (ESI FT-ICR MS)) of A. crassiflora identified fatty acids and flavonols as secondary compounds. One of the A. crassiflora fractions, 7C24 (from chloroform partition), increased H2AX phosphorylation (suggesting DNA damage), PARP cleavage, and cell cycle arrest in CCC. Kaempferol-3-O-rhamnoside and oleic acid were bioactive molecules identified in 7C24 fraction. These findings emphasize the importance of investigating bioactive molecules from natural sources for developing new anti-cancer drugs.

Keywords: Annonaceae; Asteraceae; Fabaceae; Melastomataceae; cervical cancer; cytotoxicity.

Figure 1

Effect of different natural crude extracts on viability of cervical cancer cell lines. Cellular viability was measured at 72 h by MTS assay. The results were expressed as the mean percentage ± SD of viable cells relatively to the DMSO alone (viability considered to be 100%). The half-maximal inhibitory concentration (IC₅₀) concentrations were calculated by nonlinear regression analysis using Graphpad Prism software. Data represent the mean of at least two independent experiments performed in triplicate. Concentrations of crude extracts ranged from 2.5 to 300 µg/mL. Cisplatin concentrations ranged from 0.12 to 30 µg/mL.

Figure 2

Fraction 7C24 and cell processes (DNA damage, apoptosis, and cell cycle) in SiHa and HeLa cell lines. SiHa and HeLa cells were treated with 7C24 (IC₅₀ 33.88 and 15.96 µg/mL, respectively) and cisplatin (13.01 and 9.36 µg/mL, respectively). Western blotting for phospho-H2AX, PARP, and p21 after 24 h of treatment (a). Flow cytometry of SiHa 24 h after 7C24 treatment, mean ± SD of two independent experiments (b). C + (present),—(absent). ** p < 0.01.