This study describes the extraction, preliminary characterization and evaluation of the in vitro antitumor and antioxidant activities of polysaccharides extracted from Mentha piperita (MPP). The optimal parameters for the extraction of MPP were obtained by Box-Behnken experimental design and response surface methodology (RSM) at the ratio of water to raw material of 20, extraction time of 1.5 h and extraction temperature at 80 °C. Chemical composition analysis showed that MPP was mainly composed of glucuronic acid, galacturonic acid, glucose, galactose and arabinose, and the molecular weight of its two major fractions were estimated to be about 2.843 and 1.139 kDa, respectively. In vitro bioactivity experiments showed that MPP not only inhibited the growth of A549 cells but possessed potent inhibitory action against DNA topoisomerase I (topo I), and an appreciative antioxidant action as well. These results indicate that MPP may be useful for developing safe natural health products.

Two important brown algae, Sargassum horneri and Sargassum thunbergii are widely distributed along the coastal line of China. In this study, antioxidant, angiotensin-converting enzyme (ACE) inhibitory effects, and anticoagulant activities of the methanol extracts of S. horneri and S. thunbergii were investigated and compared. Total phenolic compounds and the fucoxanthin content were determined by the spectrophotometric and HPLC analyses, respectively, to relate phytochemical content to bioactivities of two Sargassum species. The phenolic compounds of S. horneri and S. thunbergii were also analyzed by LC-MS/MS. The results showed that S. horneri displayed higher antioxidant activities compared to S. thunbergii in all antioxidant bioassays evaluated, except the DPPH radical scavenging assay. Moreover, S. horneri showed a stronger ACE inhibitory effect (IC₅₀ = 0.44 mg/mL) compared to S. thunbergii (IC₅₀ = 1.81 mg/mL). Both S. horneri and S. thunbergii significantly prolonged the activated partial thromboplastin time (APTT) in blood plasma, and the APTT-prolonging effect of S. horneri was stronger than that of S. thunbergii. Salicylic acid was identified as the main phenolic compound in S. horneri, followed by m-coumaric acid, ferulic acid, and p-coumaric acid. Furthermore, S. thunbergii contained carnosic acid and salicylic acid. The total phenolic and fucoxanthin contents are positively correlated with antioxidant, ACE inhibitory and anticoagulant activities. These results indicated that S. horneri and S. thunbergii can be used as natural sources of functional foods because of their abundant bioactive compounds.