Antioxidant, Antimicrobial and Preliminary Cytotoxic Activity of Two Mangrove Plants Caesalpinia Crista and Cynometra Ramiflora

Abstract

In this study, two mangrove shrubs Caesalpinia crista and Cynometra ramiflora from the same family (leguminosae) were selected to investigate the scientific basis for some of their traditional uses. For this purpose, bioactivities such as antioxidant, antibacterial and preliminary cytotoxic properties of these plants were evaluated using medium polar solvent (chloroform) extract and polar solvent (methanol) extract of different plant parts. In the present study, in vitro antioxidant potential was evaluated by DPPH free radical scavenging, Ferric chloride reducing power assay, Ferric reducing antioxidant power assay, Total phenolics, flavonoid and tannin content. Antimicrobial and cytotoxic activities were conducted by using disc diffusion and brine shrimp lethality bioassays respectively. Methanolic extract of C. ramiflora (stem) showed the highest free radical scavenging activity (IC₅₀: 32.65 µg/ml) and also had a capability to reduce Fe³⁺ to Fe²⁺ with reduction activity ranged from 82.697% to 326.392%. The total antioxidant capacity (84 ± 0.009 µM Fe (II)/mg) of methanolic extract of C. ramiflora (stem) was observed by FRAP assay and results suggested that methanolic extract possessed the highest antioxidant activity. Total phenolic content were estimated by the Folin-Ciocalteu colorimetric method; the total flavonoid content was estimated by aluminium chloride colorimetric method as the total tannin content was estimated by Folin-Denis method. The methanolic extract of C. ramiflora (stem) showed the highest concentration of phenolics (96.2 ± 0.010 GAE/mg of extract), flavonoid (166.4 ± 0.019 QE/mg of extract) and tannins (80.4 ± 0.009 GAE/mg of extract). The antibacterial activity of the plant C. crista extract exhibited excellent activity against Gram-positive bacteria (S. aureus and P. aurigonisa) and C. ramiflora showed good activity against both Gram-positive and Gram-negative bacteria (B. megaterium, S. typhi, S. epidermis, E. coli, P. aurigonisa, S. aureus). In case of preliminary cytotoxic activity, the significant 50% lethality concentration (LC₅₀) value was found in methanolic extract of C. crista and C. ramiflora (stem) extract. The experimental findings could be correlated with the traditional uses of these mangrove plants and showed the rational for further investigation which would be required for isolating the possible bioactive constituents responsible for such activities.