Sittichoke Janyong’s scientific contributions

Hematological investigation is an essential tool for monitoring fish health. This objective of this research was to compare morphometric traits and blood cell characteristics between two representative pelagic fish species (Ambassis nalua and A. vachelli) and one benthic species (Inegocia japonica) collected from seagrass meadows off Libong Island in Thailand, where they were exposed to human activity. Blood samples were collected and prepared using the smear technique. The erythrocytes of all observed specimens had elliptical or oval shapes. The largest erythrocytes were observed in I. Japonica. In addition, I. japonica and A. nalua had a significant degree of erythrocyte nuclear abnormalities. According to hematological profiling, lymphocytes made up the majority of leukocytes in I. japonica, followed by neutrophils. The morphometric erythrocyte data of I. japonica possibly indicated the greater oxygen requirement of fish living in demersal habitats as a result of their adaptation to the environment. The baseline parameters from the hematological data of the sampled fish will be used to monitor environmental quality.

Mangrove plants are the source of various secondary bioactive metabolites and have been used in traditional medicine for many diseases. This study aimed to investigate bioactive phytochemical components of two mangrove plants, Rhizophora mucronate and Rhizophora apiculata in the Rhizophoraceae family. Eight extracts of four parts (pod, leaf, twig, and bark) of each plant were prepared by maceration with a methanolic solvent. Phytochemical analysis was conducted through the aid of a standard test and was confirmed by quantitative analysis based on the determination of the total saponin, phenolic, and flavonoid contents. Free radical scavenging activity was studied in vitro by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) methods. Antibacterial activity was performed by the hole-plate diffusion method and determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration. The pod of R. mucronata predominantly showed the highest total saponin content [8.05 ± 0.50 mg escin equivalent (EE)/g CE], and the bark presented a great amount of phenolic and total flavonoid contents (2.12 ± 0.11 mg gallic acid equivalent/g CE and 6.73 ± 0.25 mg RU/g CE). R. mucronata showed greater free radical scavenging activity than Rhizophora apiculata at a concentration of 100 _g/ml supported by the DPPH and ABTS assays. Antibacterial screening showed that the maximum zone of inhibition was noted for R. mucronata extracts against Streptococcus agalactiae, Aeromonas hydrophila, Vibrio harveyi, and Vibrio parahemolyticus (8.50–13.56 nm). The R. mucronata pod extract had the lowest MIC to only A. hydrophila. Meanwhile, the R. mucronata bark extract had the lowest MIC to S. agalactiae and A. hydrophila. The higher antibacterial activity of R. mucronata extracts was consistent with the greater saponin, phenolic, and flavonoid contents and antioxidant activity of the extracts of these species with a significant value of p < 0.05. The present study highlighted that R. mucronata could be used as a potential source of bioactive compounds against aquatic pathogenic bacteria.

The identification of active natural compounds from plants for use as therapeutic agents for aquatic diseases could reduce the use of environmentally harmful chemicals. Lumnitzera littorea is a plant in the Combretaceae family that thrives among mangroves. Although well known in traditional medicine, there are only a few reports of the activity of various parts of this plant against aquatic pathogenic bacteria. Therefore, this work studied the phytochemical composition of the stem-bark, leaf, twig, and flower of L. littorea extracts and further investigated the antioxidant and antibacterial activities. The qualitative and quantitative analyses of phenolic and flavonoid contents were carried using the Folin-Ciocaltue and the colorimetric aluminium chloride methods, respectively. Antioxidant activity was determined by 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and 2,2/-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salts (ABTS) methods. The extracts were screened for antibacterial activity against different pathogens (Streptococcus agalactiae, Aeromonas hydrophila, Vibrio harveyi and V. parahemolyticus) using the hole-plate diffusion method. The results showed the presence of phenolic and flavonoid components in all extracts. Bark and twig extracts had greater total phenolic and flavonoid contents than those from flower and leaf extracts. Significant antioxidant activity was expressed by the bark and twig extracts. All extracts showed a wide range of antibacterial activity against the tested organisms. Bioactive substances present in L. littorea extracts exhibited antioxidant and antibacterial activities. L. littorea could be a potential source of natural bioactive compounds that could be used to develop safe and environmentally friendly pharmaceuticals against bacterial pathogens in aquatic animals.

Bruguiera cylindrica is a mangrove plant in the Rhizophoraceae family which founded in tropical regions. The dried samples of bark, leaf, pod and twig of B. cylindrica were collected and were macerated with methanol. Crude extract of each parts was determined the phytochemical screening and antibacterial activity with the aquatic pathogenic bacteria, Streptococcus agalactiae SAAQ001, Aeromonas hydrophila AHAQ001, Vibrio harveyi VHAQ001 and V. parahemolyticus by hole-plate diffusion method. Most of the plant extracts showed a wide range of antibacterial activity against gram-positive and gram-negative bacteria. In addition, minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were investigated. The results showed that the leaf and twig extracts of B. cylindrica had the lowest MIC/MBC to S. agalactiae. Phytochemical screening revealed that the B. cylindrica extracts contained a rich source of various phytochemical such as anthraquinone, terpenoids, flavonoids, saponins, phenolics and alkaloids. Terpenoid especially founded in leaf and twig supported antibacterial activity. The results presented here suggested that the presence of bioactive substances from B. cylindrica extracts was the factors responsible for bioactivity against the chosen bacterial pathogens. Also, B. cylindrica was a potential source of biologically active compounds that could be used to develop natural and bioactive pharmaceutical products against bacterial pathogens in aquatic animals. https://li01.tci-thaijo.org/index.php/rmutsvrj/article/view/245397