Antitumor and antioxidant activities of levan and its derivative from the isolate Bacillus subtilis NRC1aza

► This study reported in levansucrase isolate Bacillus subtilis NRC1aza. ► The unique feature of this isolate is its ability to produce two types of levans. ► The two levans and their derivatives characterized by strong antioxidants activity. ► SL1 induced intrinsic apoptosis pathway in liver cancer cells. ► The derivatives could be explored as promising antioxidant and antitumor agents. The novel levansucrase produced from Bacillus subtilis NRC1aza yielded two types of levan L1 and L2 with different molecular weights 85.23kDa and 31.95kDa, respectively. The levan identification was detected by paper chromatography and high-pressure liquid chromatography. The antioxidant activity of levan and their derivatives (SL1 and SL2) exhibited a strong free radical scavenging activity with DPPH. The antitumor activity of SL1 was tested against different human cancer cell lines. The cell death was explored mechanistically through evaluation of Apoptosis/necrosis ratio, DNA fragmentation, histone deacetylase activity, mitochondrial transmembrane potential (Δψm), cytochrome C release, total caspases, caspase-3, and caspase-9, and cell cycle. SL1 showed high selective cytotoxicity against HepG2 cells. SL1 led to DNA damaging and fragmentation that was associated with induced apoptosis via mitochondrial pathway, which initiated by the impairment of Δψm and then increased mitochondria, released cytochrome c, that in turn activated caspase-9 and caspase-3 and induced apoptosis.