Xanthine oxidase, α-glucosidase and α-amylase inhibitory activities of the essential oil from Piper lolot: In vitro and in silico studies.

Introduction: Piper lolot is a species of herb used as a popular food in Vietnam. Furthermore, the species has been used as a Vietnamese traditional medicine to treat many diseases. Methods: Chemical constituents in the essential oil from leaves of Piper lolot were determined using GC/MS analysis. The anti-gout and anti-diabetic activities of the essential oil were determined through the inhibitory assays against xanthine oxidase, α-glucosidase and α-amylase enzymes. In addition, molecular docking simulations were used to elucidate the inhibitory mechanism between the main compounds and the enzymes. Results: The dominant constituents of the Piper lolot essential oils were determined as ß-caryophyllene (20.6%), ß-bisabolene (11.6%), ß-selinene (8.4%), ß-elemene (7.7%), trans-muurola-4(14),5-diene (7.4%), and (E)-ß-ocimene (6.7%). The essential oil displayed xanthine oxidase, α-amylase, and α-glucosidase inhibitory activities with IC50 values of 28.4, 130.6, and 59.1 µg/mL, respectively. The anti-gout and anti-diabetic activities of the essential oil from the P. lolot species are reported for the first time. Furthermore, molecular docking simulation was consistent to in vitro experiments. Conclusion: The present study provides initial evidence that the essential oil of P. lolot may be a potential natural source to develop new diabetes preparations.

Stability Constant and Potentiometric Sensitivity of Heavy Metal-Organic Fluorescent Compound Complexes: QSPR Models for Prediction and Design of Novel Coumarin-like Ligands.

Industrial wastewater often consists of toxic chemicals and pollutants, which are extremely harmful to the environment. Heavy metals are toxic chemicals and considered one of the major hazards to the aquatic ecosystem. Analytical techniques, such as potentiometric methods, are some of the methods to detect heavy metals in wastewaters. In this work, the quantitative structure-property relationship (QSPR) was applied using a range of machine learning techniques to predict the stability constant (logßML) and potentiometric sensitivity (PSML) of 200 ligands in complexes with the heavy metal ions Cu2+, Cd2+, and Pb2+. In result, the logßML models developed for four ions showed good performance with square correlation coefficients (R2) ranging from 0.80 to 1.00 for the training and 0.72 to 0.85 for the test sets. Likewise, the PSML displayed acceptable performance with an R2 of 0.87 to 1.00 for the training and 0.73 to 0.95 for the test sets. By screening a virtual database of coumarin-like structures, several new ligands bearing the coumarin moiety were identified. Three of them, namely NEW02, NEW03, and NEW07, showed very good sensitivity and stability in the metal complexes. Subsequent quantum-chemical calculations, as well as physicochemical/toxicological profiling were performed to investigate their metal-binding ability and developability of the designed sensors. Finally, synthesis schemes are proposed to obtain these three ligands with major efficiency from simple resources. The three coumarins designed clearly demonstrated capability to be suitable as good florescent chemosensors towards heavy metals. Overall, the computational methods applied in this study showed a very good performance as useful tools for designing novel fluorescent probes and assessing their sensing abilities.

Pharmacological Properties, Volatile Organic Compounds, and Genome Sequences of Bacterial Endophytes from the Mangrove Plant Rhizophora apiculata Blume.

Mangrove plant endophytic bacteria are prolific sources of bioactive secondary metabolites. In the present study, twenty-three endophytic bacteria were isolated from the fresh roots of the mangrove plant Rhizophora apiculata. The identification of isolates by 16S rRNA gene sequences revealed that the isolated endophytic bacteria belonged to nine genera, including Streptomyces, Bacillus, Pseudovibrio, Microbacterium, Brevibacterium, Microbulbifer, Micrococcus, Rossellomorea, and Paracoccus. The ethyl acetate extracts of the endophytic bacteria's pharmacological properties were evaluated in vitro, including antimicrobial, antioxidant, α-amylase and α-glucosidase inhibitory, xanthine oxidase inhibitory, and cytotoxic activities. Gas chromatography-mass spectrometry (GC-MS) analyses of three high bioactive strains Bacillus sp. RAR_GA_16, Rossellomorea vietnamensis RAR_WA_32, and Bacillus sp. RAR_M1_44 identified major volatile organic compounds (VOCs) in their ethyl acetate extracts. Genome analyses identified biosynthesis gene clusters (BGCs) of secondary metabolites of the bacterial endophytes. The obtained results reveal that the endophytic bacteria from R. apiculata may be a potential source of pharmacological secondary metabolites, and further investigations of the high bioactive strains-such as fermentation and isolation of pure bioactive compounds, and heterologous expression of novel BGCs in appropriate expression hosts-may allow exploring and exploiting the promising bioactive compounds for future drug development.

In vitro study on α-amylase and α-glucosidase inhibitory activities of a new stigmastane-type steroid saponin from the leaves of Vernonia amygdalina.

Using various chromatographic separations, four compounds, including one new steroid saponin named vernoamyoside E (1), were isolated from the leaves of the Vietnamese medicinal plant Vernonia amygdalina Delile (Asteraceae). Their structures were established by spectroscopic methods such as 1D- and 2D-NMR, HR-ESI-MS, and HPLC analysis. The inhibitory activities against α-glucosidase and α-amylase of the isolated compounds from V. amygdalina were reported for the first time. The results indicated that compound 1 significantly inhibited both against α-amylase and α-glucosidase activity.

Coral and Coral-Associated Microorganisms: A Prolific Source of Potential Bioactive Natural Products.

Marine invertebrates and their associated microorganisms are rich sources of bioactive compounds. Among them, coral and its associated microorganisms are promising providers of marine bioactive compounds. The present review provides an overview of bioactive compounds that are produced by corals and coral-associated microorganisms, covering the literature from 2010 to March 2019. Accordingly, 245 natural products that possess a wide range of potent bioactivities, such as anti-inflammatory, cytotoxic, antimicrobial, antivirus, and antifouling activities, among others, are described in this review.

New Alkaloids and Anti-inflammatory Constituents from the Leaves of Antidesma ghaesembilla.

Using various chromatographic methods, two new alkaloids, antidesoic acids A (1) and B (2) along with fourteen known compounds (3-16) were isolated from the leaves of Antidesma ghaesembilla Gaertn. Their chemical structures were elucidated by physical and chemical methods. All the isolated compounds were evaluated for their inhibitory activity on LPS-stimulated nitric oxide (NO) production in BV2 cells and RAW 264.7 macrophages. Bisflavone 8 significantly inhibited LPS- stimulated NO production in BV2 cells and RAW 264.7 macrophages with IC50 values of 5.4 and 8.0 µM, respectively. Compounds 1-3, 7, 10, 12, 14, and 16 showed moderate inhibitory activities with IC50 values ranging from 11.7 to 77.4 µM.

New Lignans from Antidesma hainanensis Inhibit NO Production in BV2 Microglial Cells.

Two new lignans (7S,7'R,8S,8'R)-3,3'-dimethoxy-7,7'-epoxylignan-4,4',9-triol 4-O-ß-D-glucopyranoside (1) and 9-O-formylaviculin (2) together with other thirteen known secondary metabolites were isolated from the leaves of Antidesma hainanensis. Their chemical structures were determined using NMR, electrospray ionization (ESI)-MS, circular dichroism (CD) spectroscopic methods, and as well as by comparison with those reported in the literature. Neuro-inflammatory activity of isolated compounds was evaluated by their inhibition on nitric oxide (NO) production in activated BV2 microglial cells. At concentration of 40 µM, compounds 1-3, 5, 7, 8, 9, 14, and 15 exhibited inhibitory effects over 50%, suggesting that they could be potential candidate drugs for the cure of neuro-inflammation. In addition, compounds 1, 8, 14, and 15 significantly inhibited 16.23, 27.76, 21.23, and 29.44% NO production at diluted concentration as low as 2.5 µM.