## 3 Results
### Modulation of Cytotoxicity
Extracts with the highest reversal factor against MCF-7/Sens (RF = 362.50). The result is similar or superior to the one observed in the reserpine, positive control (RF 32.95 for MCF-7/Sens and 3.14 for MCF-7/Vin\({}^{+}\)), a cytotoxic positive efflux pump control [29; 47; 48]. Additionally, all the extracts showed a modulation effect against MCF-7/Vin\({}^{-}\) (RF from 0.47- to 4.05-fold), except the stem and leaf extracts of plants grown on black soil obtained using ME and SFE, respectively. These extracts had a lower RF score than the positive control (RF 22.42-fold). These results were in line with those of [PERSON] et al. [6]. They mentioned that herbal extracts such as _Solanum nigum_ and _Claviceps purpnea_, combined with chemotherapy drugs, attenuated the resistance to the drug and exerted chemoprotective actions. The reversal activity of our samples could be due to an additive synergism. Natural compounds applied with chemotherapy drugs increase the cytotoxic effects of known anticancer agents. They exert their functions in multiples ways, e.g., through autophagy induction, via regulating pro-inflammatory cytokines such as tumor necrosis factor \(\alpha\) (TNF-\(\alpha\)) and interferon \(\gamma\) (IFN-\(\gamma\)), by modulating the tumor micro-environment, or by regulating the expression or activity of the transcription nuclear factor kappa B (NF-\(\kappa\)B). NF-\(\kappa\)B seems to be an indicator for determining the potency of chemotherapeutic cytotoxicity [6; 49]. In the extracts studied, further research is necessary to determine the mechanisms of action used by the compounds present in the samples to potentiate the vinblastine cytotoxicity. In addition, the Pearson correlation coefficient calculated for the polyphenol content previously quantified by [PERSON] et al. [17], and the cytotoxicity modulation of the samples evaluated in the present research, showed a very low correlation with values ranging between \(-\)0.51 and 0.06 for modulation against MCF-7/Sens and with values ranging between \(-\)0.88 and 0.16 for modulation against MCF-7/Vin\({}^{-}\). For modulation against MCF-7/Vin\({}^{+}\), we obtained values from \(-\)0.51 to 0.58, a moderately positive correlation between the cytotoxicity modulation of the samples and gallic acid and catechin content (0.48 and 0.49, respectively) and a strong positive correlation between modulation and protocatechuic acid (0.58). Hence, the modulation of the cytotoxicity against MCF-7/Sens  
Figure 4: Modulation assay of vinblastine with stems of plants grown on black soil and peduncles of plants grown on red soil extracts obtained using maceration against MCF-7/Vin\({}^{+}\)-resistant cell line. SBS ME: extract with the highest reversal factor against MCF-7/Vin\({}^{+}\) (RF = 7.78). could be explained by other types of compounds present in the samples [22], such as terpenoids or coumarins [6; 7]. Gallic acid, catechin, and protocatechu acid could be responsible for the cytotoxicity modulation against MCF-7/Vin\({}^{+}\). On the other hand, the methanol maceration method seems to observe the extraction of compounds with anticancer potential from _Capsicum chinense_ by-products. Thus, the compounds responsible for these biological activities are probably highly polar and thermolabile [36; 37; 50] For this reason, Soxhlet with ethanol and extraction by supercritical fluids with CO\({}_{2}\) + ethanol did not extract them. Additionally, there were significant differences due to the type of soil in which the plants were grown for extracts having antiproliferative activity and modulating effect on cytotoxic activity. Black soil used for _C. chinense_ by-products showed cytotoxicity against HCT-15 cancer cells and cytotoxicity modulation on MCF-7/Vin\({}^{+}\), while the red soil showed to potentiate the cytotoxicity of vinblastine against MCF-7/Sens.