In Vitro and In Vivo Antitumor Activity of a Chloroform Partition from Ibervillea sonorae (S. Watson) Greene Endophytic Bacillus subtilis Extracts

Cancer is a complex disease due to its high variability and resistance to conventional treatments. The search for new therapies has prompted the study of less invasive natural sources, such as endophytic bacteria from medicinal plants. <i>Bacillus subtilis</i> is known to produce bioactive metabolites with promising pharmacological properties. This study evaluated the antitumor activity of the endophyte <i>B. subtilis</i> from <i>Ibervillea sonorae</i> against murine L5178Y-R lymphoma cells within in vitro and in vivo models. <i>B. subtilis</i> methanol extract was fractionated in hexane, chloroform, and methanol, with the chloroform partition showing the highest tumor cell growth inhibition (IC₅₀ = 34.62 ± 0.180 µg/mL) and the highest selectivity index (SI = 15.53) when compared with the hexane and methanol partitions. The in vivo study showed that mice treated with 10 mg/kg of the chloroform partition significantly (<i>p</i> < 0.01) reduced the tumor volume and weight without affecting tumor-free body weight. The maximum tolerated dose test indicated that 10 mg/kg was safe and well tolerated. These results indicate that <i>B. subtilis</i> may be a promising source of selective antitumor compounds.