Acetylcholinesterase-inhibiting activity of marinoquinoline A (1), a new pyrroloquinoline from a novel species of a marine gliding bacterium Rapidithrix thailandica, was assessed (IC 50 4.9 μM). Two related pyrrole derivatives, 3-(2'-aminophenyl)-pyrrole (3) and 2,2-dimethyl-pyrrolo-1,2-dihydroquinoline (4), were also isolated from two other strains of R. thailandica. The isolation of 3 from a natural source is reported here for the first time. Compound 4 was proposed to be an isolation artifact derived from 3.The two isolated compounds were virtually inactive in the acetylcholinesterase-inhibitory assay (enzyme inhibition < 30% at 0.1 g L -1 ).

Neuropeltis racemosa Wall. (Convolvulaceae) is wildly distributed in Asia. Its stem is used as the component in traditional Thai recipes for treatments of muscle rigidity, skin disorder, dysentery, and hypoglycemia. However, the chemical constituents and biological activities of N. racemosa have not been reported. From a screening assay, N. racemosa stem crude extract showed the potent effect on alpha-glucosidase inhibition at 2 mg/mL as 96.09%. The bioassay-guiding isolation led to 5 compounds that were identified by spectroscopic techniques as scopoletin (1), syringic acid (2), methyl 3-methyl-2-butenoate (3), N-trans-feruloyltyramine (4), and N-trans- coumaroyltyramine (5). Compounds 1, 4, and 5 exhibited an IC50 of 110.97, 29.87, and 0.92 µg/mL, respectively, while the IC50 of positive standard, acarbose was 272.72 µg/mL. Kinetic study showed that compound 1 performed as the mixed-type inhibition mechanism, whereas compounds 4 and 5 displayed the uncompetitive inhibition mechanism. The docking study provided the molecular understanding of isolated aromatic compounds (1, 2, 4 and 5) to alpha-glucosidase. Hence, this study would be the first report of isolated compounds and their anti-alpha-glucosidase activity with the mechanism of action from N. racemosa. Thus, these active compounds will be further studied to be the lead compounds among natural antidiabetic drugs.

Skin disorders are a worldwide health problem that normally affect human life. A traditional healer is an important expert in researching notable medicinal plants for skin disease treatment. This study aimed to determine the traditional knowledge and the use of medicinal plants for the treatment of skin diseases among traditional healers in the Songkhla province, Thailand. The ethnobotanical information was collected from experienced traditional healers by semi-structured interviews and participant observations. Plant specimens were also collected and identified using the standard taxonomic method. The data were analyzed by interpretation and descriptive statistics. Twenty-five polyherbal formulations for the treatment of skin diseases were obtained from traditional healers with at least 10 years of experience. A total of 66 plant species in 38 families were documented. Leaves and trees were the most commonly employed plant parts and plant habits included in the herbal remedies, respectively. Fabaceae, Rubiaceae, and Zingiberaceae were the majority of the cited families. Oryza sativa L. and Zingiber montanum (J. Koenig) Link ex A.Dietr. were the most preferred plants combined in the prescriptions, which had the highest use value (UV = 0.83). The highest relative frequency of citation was represented by Curcuma longa L., Eurycoma longifolia Jack, Knema globularia (Lamk.) Warb, and Senna siamea (Lam.) Irwin & Barneby. (0.55 each). This research suggests the importance of traditional healers in the healing of skin diseases with herbal remedies. A variety of medicinal plants are used in the prescriptions for the treatment of skin disorders in the Songkhla province, in the south of Thailand. Pharmacological and toxicological activities as well as phytochemical constituents of polyherbal remedies should be further investigated to scientifically verify further applications of widely practiced herbal medicines.

Solanum stramonifolium Jacq. (Solanaceae) is widely found in South East Asia. In Thailand, it is used as vegetable and as a component in traditional recipes. The results of an alpha-glucosidase inhibitory screening test found that the crude extract of S. stramonifolium inflorescence exhibited the potential effect with IC50 81.27 μg/mL. The separation was performed by the increasing solvent polarity method. The ethyl acetate, ethanol, and water extracts of S. stramonifolium inflorescence showed the synergistic effect together with acarbose standard. The phytochemical investigation of these extracts was conducted by chromatographic and spectroscopic techniques. Six flavonoid compounds, myricetin 3, 4′, 5′, 7-tetramethyl ether (1), combretol (2), kaempferol (3), kaempferol 7-O-glucopyranoside (4), 5-hydroxy 3-7-4′-5′-tetramethoxyflavone-3′-O-glucopyranoside (5), and a mixture (6) of isorhamnetin 3-O-glucopyranoside (6a) and astragalin (6b) were isolated. This discovery is the first report of flavonoid-glycoside 5. Moreover, the selected flavonoids, kaempferol and astragalin, were representatives to explore the mechanism of action. Both of them performed mixed-type inhibition. The molecular docking gave a better understanding of flavonoid compounds’ ability to inhibit the alpha-glucosidase enzyme.