Identification of Chemical Profiles and Biological Properties of Rhizophora racemosa G. Mey. Extracts Obtained by Different Methods and Solvents

Mangrove forests exemplify a multifaceted ecosystem since they do not only play a crucial ecological role but also possess medicinal properties. Methanolic, ethyl acetate and aqueous leaf and bark extracts were prepared using homogenizer-assisted extraction (HAE), infusion and maceration (with and without stirring). The different extracts were screened for phytochemical profiling and antioxidant capacities in terms of radical scavenging (DPPH, ABTS), reducing potential (CUPRAC, FRAP), total antioxidant capacity and chelating power. Additionally, R. racemosa was evaluated for its anti-diabetic (α-amylase, α-glucosidase), anti-tyrosinase and anti-cholinesterase (AChE, BChE) activities. Additionally, antimycotic and antibacterial effects were investigated against Eescherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium, Listeria monocytogenes, Enterobacter cloacae, Bacillus cereus, Micrococcus luteus, Staphylococcus aureus, Aspergillus fumigatus, Aspergillus niger, Trichoderma viride, Penicillium funiculosum, Penicillium ludwigii and Penicillium verrucosum. Finally, based on phytochemical fingerprint, in silico studies, including bioinformatics, network pharmacology and docking approaches were conducted to predict the putative targets, namely tyrosinase, lanosterol-14-α-demethylase and E. coli DNA gyrase, underlying the observed bio-pharmacological and microbiological effects. The methanolic leave and bark extracts (prepared by both HAE and maceration) abounded with phenolics, flavonoids, phenolic acids and flavonols. Results displayed that both methanolic leaf and bark extracts (prepared by HAE) exhibited the highest radical scavenging, reducing potential and total antioxidant capacity. Furthermore, our findings showed that the highest enzymatic inhibitory activity recorded was with the tyrosinase enzyme. In this context, bioinformatics analysis predicted putative interactions between tyrosinase and multiple secondary metabolites including apigenin, luteolin, vitexin, isovitexin, procyanidin B, quercetin and methoxy-trihydroxyflavone. The same compounds were also docked against lanosterol-14α-demethylase and E. Coli DNA gyrase, yielding affinities in the submicromolar-micromolar range that further support the observed anti-microbial effects exerted by the extracts. In conclusion, extracts of R. racemosa may be considered as novel sources of phytoanti-oxidants and enzyme inhibitors that can be exploited as future first-line pharmacophores.

Keywords: anti-microbial activity; enzyme inhibition; homogenizer-assisted extraction; in silico studies; mangrove; phytoanti-oxidants; phytochemical.