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Introduction: This research aims to evaluate the anti-diabetic activity of the extracts from different parts of Cratoxylum formosum subsp. formosum.Methods: The in vitro inhibitory activities of the hexane (HEX), dichloromethane (DCM) and ethyl acetate (EtOAc) extracts from the flowers, leaves, roots and stems on pancreatic α-amylase (pAA), Saccharomyces α-glucosidase (SAG), rat intestinal maltase (rIM), and sucrase (rIS) were investigated. Results: The DCM and EtOAc extracts from the flowers (IC50 5.4 ± 1.5 and 10.5 ± 0.6 µg/mL) displayed the similar inhibitory activities as acarbose (IC50 7.2 ± 0.4 µg/mL) in the pAA assay. The inhibitory activities of the DCM and EtOAc extracts from the flowers (IC50 56.7 ± 8.9 and 20.4 ± 0.4 µg/mL), EtOAc extract from leaves (IC50 45.0 ± 3.5 µg/mL), DCM and EtOAc extracts from roots (IC50 35.0 ± 6.7 and 16.7± 3.6 µg/mL), and EtOAc extract from stems (IC50 31.1 ± 7.3 µg/mL) were more potent than acarbose (IC50 431.4 ± 16.7 µg/mL) on SAG inhibitory assay (P<0.05). In the rIM assay, DCM and EtOAc extracts from the flowers (IC50 8.5 ± 0.2 and 12.4 ± 0.3 µg/mL) exhibited stronger inhibitory activity than acarbose (IC50 38.5 ± 7.2 µg/mL) (P<0.05). Moreover, the inhibitory activity of DCM extract from the flowers (IC50 16.9 ± 1.5 µg/ mL) was comparable to the acarbose (IC50 15.5 ± 1.2 µg/mL) on rIS assay. Conclusion: The DCM and EtOAc extracts from the flowers were more active than the leaves, roots and stems in the inhibition of our defined target enzymes.

Context: Caesalpinia sappan and Ochna integerrima are two native plants of Thailand and distributed widely throughout the country. Recently, water extracts from the stem bark of C. sappan and O. integerrima were found to exhibit potently antibacterial property but the antibacterial mechanism of action toward target bacteria has not been investigated yet. Aims: To study time-kill kinetic and the mechanism of action of C. sappan and O. integerrima waterextracts toward target bacteria. Methods: The time-kill kinetic study of bacteriostatic or bactericidal activity against Gram-positive and Gram-negative pathogenic bacteria within 24 h experiment was conducted and the mechanism of action on cell morphology of the target bacteria by using scanning electron microscopy (SEM) were investigated. Results: Both of the C. sappan and O. integerrima water extracts possessed bacteriostatic or bactericidal activity toward six tested pathogenic bacteria. The bacteriostatic or bactericidal activity depending on bacterial strains and the test concentrations (0.5, 1 and 2 × MIC) of these two extracts to the tested bacteria were observed. The bactericidal activity against all of the tested bacterial was evinced at 2 × MIC. The morphological alterations of the target bacterial cells of changing the cell size (decreased and increased), cell lysis and having cell cavity were detected by SEM after the treatment with C. sappan and O. integerrima water extracts. Conclusions: The water extracts from the stem bark of C. sappan and O. integerrima exhibited bactericidal activity by changing the cell size, cell lysis and cell cavity of the tested bacteria cell morphology.