Antioxidant activity of caffeic acid: thermodynamic and kinetic aspects on the oxidative degradation pathway

Caffeic acid is a phenolic secondary metabolite from plants, which is known for its antioxidant properties. The effective mitigation of methanol-induced oxidative stress by caffeic acid depends on the direct radical scavenging as well as the formation of new metabolites via oxidative degradation. Herein, thermodynamic and kinetic aspects of the oxidative degradation pathway of caffeic acid in the presence of radical CH₃O^• and its isomer, ^•CH₂OH are discussed for the first time, employing density functional theory (DFT). The direct radical scavenging activity of caffeic acid against these radicals is verified via hydrogen atom transfer (HAT) and radical adduct formation (RAF) mechanisms. HAT is predicted to be more feasible than RAF mechanism as per the computed data. Additionally, energetic details of the proposed oxidative degradation pathway of radical adduct intermediates toward the formation of a cyclic metabolite is analyzed. Kinetic studies indicated a significant tunneling contribution to the H abstraction pathways having high activation barriers. Further, our results imply that the newly formed metabolites exhibit comparable antioxidant activity with that of caffeic acid.

Curcumin analogues with improved antioxidant properties: A theoretical exploration

Curcumin, a ubiquitous dietary molecule, is a versatile antioxidant that fights against free radicals. The antioxidant activity of curcumin and its structural analogues such as hispolon, halfcurcumin and polyhydroxycurcumin is analyzed using density functional theory (DFT). The thermochemical parameter, bond dissociation enthalpy (BDE) is used to analyse the propensity of radical attack. The hydrogen atom transfer (HAT) energetics for the hydroxyl groups of the antioxidant molecules with •OH and •OOH in both gas and solvent media are explored. Based on ourresults, hispolon and polyhydroxycurcumin characterized by multiple hydroxyl groups arranged in ortho dihydroxy fashion are good radical scavengers. Halfcurcumin exhibited comparatively similar activity as that of curcumin. The absorption properties of these molecules are in good agreement with the reported experimental findings. The molecular docking studies revealed that these antioxidants can indirectly control the oxidative stress by favourably interacting with the pro-oxidant enzyme like xanthine oxidase.

Hydroxyl radical scavenging activity of melatonin and its related indolamines

The hydroxyl radical (•OH) scavenging activities of Melatonin, an endogenously produced neurohormone and its related indolamines like N-acetyl tryptophan (NAT) and N-acetyl serotonin (NAS) have been investigated using density functional theory. The mechanism involves 4 steps: initial radical addition to position-3 of the indole ring, keto-amine to enol-imine tautomerization, cyclisation, and finally, addition of a second •OH leading to a cyclic end product. Incorporation of an explicit water molecule in tautomerization step leads to a significant reduction in the barrier of this step, so that the subsequent cyclisation step becomes rate-limiting. In agreement with the very high reactivity of •OH, the initial and final addition of •OH to indolamine are found to be barrierless. Radical adduct formed in the initial step was found to be very stable due to the extensive conjugation present in the substrate. Our calculations show that melatonin is the most effective radical scavenger among the three molecules chosen. NAS was found to exhibit antiradical property comparable to that of melatonin. In contrast to the general observation of reduced antioxidant activity of tryptophan, a non-natural derivative of tryptophan used here (NAT) is found to have good radical scavenging activity. This work further implies that non-natural derivatives of indolamines might as well be useful in the detoxification of free radicals as they exhibit almost comparable antioxidant efficiency as that of melatonin.

Managing ascites in patients with chronic liver disease

This article discusses the pathophysiology of ascites, a complication associated with chronic liver disease. The diagnosis and grading of ascites and assessment of patients with the condition are explored. In addition, the nursing and medical management of ascites is discussed, and recommendations for interdisciplinary working and education are suggested. Nursing knowledge of this complication is essential to ensure that patients with ascites are cared for effectively and that their comfort is maximised.

Physico-chemical and microbial characteristics of the coral reef environment of the Gulf of Mannar marine biosphere reserve, India

Investigation on physico-chemical parameters and bacteial characteristics of the coral reef environs of the Gulf of Mannar biosphere reserve was studied. The study found the influence of different physico-chemical parameters on one another and also on the distribution of the total heterotrophic bacteria (THB) in the coral reef areas. Nutrients exhibited considerable seasonal and spatial variations with influence on the bacterial population. Coral reef areas recorded higher bacterial population density both in water (3.5 to 18 x 10(5) CFU ml(-1)) and sediment (1 to 14 x 10(7) CFU g(-1)) samples than the non coral reef areas (3.4 to 10.5 x 10(4) CFU ml(-1) in water and 0.9 to 7 x 10(6) CFU g(-1)). The study also found the dominance of gram negative groups at all the three stations (64.73, 63,5 and 72.59%) with Pseudomonas contributing maximum number of strains in all the samples. In addition Vibrio, Aeromonas, Flavobacterium, Cytophaga, Enterobacter and Alcaligenes were also recorded. The gram positive group was represented by Bacillus, Micrococcus, Arthrobacter and Corynebacterium. The genetic composition of THB isolated from the coral mucus revealed the presence of Vibrio and Micrococcus in all the coral mucus.

Effect of probiotics on bacterial population and health status of shrimp in culture pond ecosystem

The artificially manufactured probiotics having beneficial bacteria, Bacillus spp. was applied regularly in a modified extensive shrimp (Penaeus monodon) culture pond, located on the bank of Vellar estuary, Parangipettai. The populations of total heterotrophic bacteria (THB), beneficial bacteria (Bacillus spp.) and pathogenic bacteria (vibrios) were monitored in water and sediment of the pond. The results were compared with a control pond, situated in the same location having same water spread area, stocking density, species managed with same technologies and optimum environmental parameters in which no probiotic was applied. The populations of THB and Bacillus spp. in the experimental pond increased and the vibrios decreased after each application of probiotics. But the result of the control pond showed an increasing trend of the populations of THB, Bacillus spp. and vibrios towards days of culture. The control pond had lower levels of THB and Bacillus spp. and higher levels of vibrios than the probiotic applied (experimental) pond. Also the probiotics maintained optimum transparency and low organic load in the experimental pond as compared to control. In general, water and sediment had almost equal number of Bacillus spp. and vibrios, but sediment had higher THB load than water. The applications of probiotics lesser pathogenic vibrios and enhance beneficial bacilli in the culture leading to improved water quality, promoted growth and survival rates and increased the health status of the shrimp without stress and disease outbreaks. Thus the application of probiotics could lead to disease-free and profitable shrimp culture operations which will be helpful for shrimp farmers as most of them are now-a-days severely affected by microbial diseases.

Antibiotic-resistant Vibrio cholerae in Parangipettai coastal environs, south east India

This study was undertaken to determine the comparative incidence of drug-resistant Vibrio cholerae non-01 in the environmental samples (water, sediment, and plankton) and in the seafood samples (finfish, shellfish, and crustacean) of estuarine, coastal, and mangrove communities. A total of 770 V. cholerae isolates were examined--all of the strains were sensitive to 100% against cephalothin (30 mcg), chloramphenical (30 mcg), and polymyxin-B (300 mcg). However, all of the strains isolated form environmental and seafood samples showed higher resistance (> 25%) to oxytetracycline, streptomycin, sulphadiazine, tetracycline, and to streptomycin, sulphadiazine, and tetracycline, respectively. The percentage of strains resistant to other antimicrobial substances depended on the antibiotic and on the isolation source. Among the isolates tested, a significantly higher number of drug-resistant bacteria was found to occur in water and finfish samples.

Preliminary investigation on antibacterial activity of some marine diatoms

Seven species of marine diatoms were cultured under defined laboratory conditions. Air dried algal powder was used for extraction with different solvents in sequence. The algal extracts were tested against various bacteria by paper disc method. Nitzschia longissma, Skeletonema costatum and Biddulphia sinensis were effective against the test bacteria. Hemidiscus hardmannianus, Coscinodiscus centralis and Asterionella japonica showed moderate antibacterial activity. Pleurosigma elongatum exhibited no activity. The antibacterial substances were fully extracted by the organic solvents. Only in the active algal species, was activity noted in the aqueous extracts.