No abstract

The aim of this work is to purify and characterise bioactive molecules from various solvent extracts prepared with the leaves of Rhizophora mucronata, a mangrove plant. In vitro assessment of antibacterial activity of n-hexane, diethyl ether, ethanol, and aqueous extracts (AEs) against Bacillus subtilis (0.4 ± 0.1, 1.1 ± 0.3, 0.9 ± 0.1, and 1.2 ± 0.7 mm), Staphylococcus aureus (1.2 ± 0.1, 2.3 ± 0.5, 3.2 ± 1.2, and 4.4 ± 1.7 mm), Klebsiella pneumoniae (0.5 ± 0.3, 1.7 ± 0.4, 3.9 ± 1.4, and 3.9 ± 0.9 mm), and Pseudomonas aeruginosa (0.2 ± 0.1, 2.5 ± 0.6, 3.7 ± 0.5, and 4.2 ± 1.3 mm) has proven to act as potent similar to that of commercial antibiotic. Corresponding to antibacterial activity result, antioxidant activity was also higher for AE (75.97% ± 0.5%) compared to remaining extracts (73.77% ± 2.5%, 69.99% ± 0.4%, and 65.24% ± 1.8%) at a concentration of 500 μg·mL−1. Considering both the activities, AE was selected for separation of bioactive molecule by deploying two purification techniques – column chromatography and preparative thin layer chromatography consecutively. After purification, the sample was injected into mass spectrometer and the presence of N-p-coumaroyltyramine and luteolin with excellent antibacterial and antioxidant properties (13.1 ± 2.2 mm and 80.9% ± 2.3%, respectively) were recognised. Further, in vivo investigations on Catla catla fingerlings infected with P. aeruginosa indicated that partially purified extracts cured the infection and resulted in a 100% survival rate.

Incidence of various dreadful microbial infections and the development of antibiotic resistance by infection causative microbes are the main reasons for reducing aquaculture productivity. Hence, there is an immense need for the discovery of alternative and efficient treatment for quick recovery of diseased fishes. In the present study, Suaeda maritima leaf extracts (hexane, diethyl ether, ethanol, and water) were screened for in vitro and in vivo antibacterial and antioxidant activities. Out of all the four extracts, ethanolic extract showed highest antibacterial activity against S. aureus (4.9 ± 1.3 mm), B. subtilis (1.6 ± 0.3 mm), K. pneumoniae (4.2 ± 1.8 mm), and P. aeruginosa (4.1 ± 1.2 mm). Similarly, antioxidant activity was also higher for ethanolic extract (500 µg/mL) based on DPPH radical scavenging ability (71.6 ± 1.4%) and reducing potential (149 μg/mL) assays. Further, ethanolic extract was purified consecutively via column chromatography and preparative TLC where an active fraction was selected based on highest antibacterial (10.1 ± 1.4 mm) and antioxidant properties (82.3 ± 2.8%). Active fraction was loaded onto mass spectroscopy and identified the presence of four active constituents such as 1,2,9,10-tetramethoxy-6-methyl-5,6,6a,7-tetrahydro-4H-dibenzo[de,g]quinolin-3-yl) methanol; 3',7-Dimethoxy-3-hydroxyflavone; Saponin and (19R)9acetyl19hydroxy10,14dimethyl20oxopentacyclo[11.8.0.0 < 2,10 > .0 < 4,9 > .0 < 14,19 >]henicos-17-yl-acetate. Besides, in vivo studies were conducted on Catla catla fingerlings infected with P. aeruginosa under laboratory conditions. The fingerlings were segregated into 5 groups, among which group 4 and 5 were treated with crude and purified extracts. Both the extracts were efficient in treating infected fingerlings and recorded 100% survival rate which is even better than group-3 treated with a synthetic antibiotic (77%). Hence, S. maritima leaf extract can be considered as a possible alternative medicine in aquaculture.

Incidence of various dreadful microbial infections and the development of antibiotic resistance by infection causative microbes are the main reasons for reducing aquaculture productivity. Hence, there is an immense need for the discovery of alternative and efficient treatment for quick recovery of diseased fishes. In the present study, Suaeda maritima leaf extracts (hexane, diethyl ether, ethanol, and water) were screened for in vitro and in vivo antibacterial and antioxidant activities. Out of all the four extracts, ethanolic extract showed highest antibacterial activity against S.aureus (4.9±1.3 mm), B.subtilis (1.6±0.3 mm), K.pneumonia (4.2±1.8 mm), and P.aeruginosa (4.1±1.2 mm). Similarly, antioxidant activity was also higher for ethanolic extract (500 µg/ml) based on DPPH radical scavenging ability (71.6±1.4 %) and reducing potential (149 μg/mL) assays. Further, ethanolic extract was purified consecutively via column chromatography and preparative TLC where an active fraction was selected based on highest antibacterial (10.1±1.4 mm) and antioxidant properties (82.3±2.8 %). Active fraction was loaded onto mass spectroscopy and identified the presence of four active constituents such as 1,2,9,10-tetramethoxy-6-methyl-5,6,6a,7-tetrahydro-4H-dibenzo[de,g]quinolin-3-yl) methanol; 3',7-Dimethoxy-3-hydroxyflavone; Saponin and (19R)9acetyl19hydroxy10,14dimethyl20oxopentacyclo[11.8.0.0<2,10>.0<4,9>.0<14,19>]henicos-17-yl-acetate. Besides, in vivo studies were conducted on Catla catla fingerlings infected with P. aeruginosa under laboratory conditions. The fingerlings were segregated into 5 groups, among which group 4 and 5 were treated with crude and purified extracts. Both the extracts were efficient in treating infected fingerlings and recorded 100% survival rate which is even better than group-3 treated with a synthetic antibiotic (77%). Hence, S. maritima leaf extract can be considered as a possible alternative medicine in aquaculture