Antibacterial Activity of Lupinifolin from Derris reticulata and Its Effect on Cytoplasmic Membrane of Methicillin Resistant

Lupinifolin from Derris reticulata Craib. was extracted with hexane by Soxhlet extractor and purified by crystallization. The yellow needle-shaped lupinifolin crystals were identified and confirmed by nuclear magnetic resonance (NMR) spectra and Liquid chromatography mass spectrometry (LC/MS). The lupinifolin showed minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 8 and 16 µg/ml against Methicillin resistant S. aureus (MRSA), respectively. The flow cytometry (FCM) was performed to determine the alteration of cytoplasmic membrane (CM) permeability of MRSA by using Propidium iodide (PI) 5 µg/ml as an indicator for bacterial membrane integrity. It was found that the bacterial CM permeability was effected by lupinifolin with the MIC of 8 µg/ml comparable to the control when investigated by Propidium iodide intensity. Additionally, DNA laddering assay was carried out to evaluate apoptosis in bacterial cells. It was shown that the lupinifolin has no effect on DNA fragmentation.

Ultrasound-Assisted Extraction for Simultaneous Quantitation of Potential Sweetening Compounds from Derris reticulata Aqueous Extracts: A Response Surface Methodology Approach

Background: Derris reticulata or Oi Sam Saun is a highly sweet Thai plant, rich in bioactive compounds, and widely used for its medicinal properties. In this study, sweet aqueous extracts from the stems of Oi Sam Saun were extracted using ultrasound-assisted extraction (UAE). Phenolic, flavonoid, and sugar compound extraction was optimized using the Box-Behnken design (BBD) and response surface methodology (RSM). Methods: Three independent variables—extraction temperature (40–80°C), sonication time (20–60 min), and extraction ratio (1:10–1:30 g/mL)—were investigated, and the optimal condition was used to determined phenolics, flavonoid and 18β-glycyrrhetinic acid by High performance liquid chromatography-diode array detector (HPLC-DAD). Sensory evaluation was also performed.Results: The values of 84°C, 64 min, and ratio 1:8 g/mL were found to be optimal. Under these conditions, experimental values were well correlated with predicted values, and phenolic, flavonoid, and sugar contents were determined as 0.4725 mgGAE/gDW, 0.1489 ± 0.033 mgCE/gDW, and 4.802 ± 0.651 mg/gDW, respectively. Gallic acid, p-coumaric acid, quercetin, and kaempferol was also found in optimal condition. Moreover, the extract contained 18β-glycyrrhetinic acid (0.529 ± 0.002 mg/100 mg) and was 166 times sweeter than sucrose.Conclusion: High level of phenolics, flavonoids and sugars was detected in optimal condition of the extract. Therefore, this Thai medicinal plant, which has several pharmacological benefits, is newly potentially and applicable as a sweetening agent or sugar substitute in foods.