α-Amylase and dipeptidyl peptidase-4 (DPP-4) inhibitory effects of Melicope latifolia bark extracts and identification of bioactive constituents using in vitro and in silico approaches.

CONTEXT: Melicope latifolia (DC.) T. G. Hartley (Rutaceae) was reported to contain various phytochemicals including coumarins, flavonoids, and acetophenones. OBJECTIVE: This study investigates the antidiabetic and antioxidant effects of M. latifolia bark extracts, fractions, and isolated constituents. MATERIALS AND METHODS: Melicope latifolia extracts (hexane, chloroform, and methanol), fractions, and isolated constituents with varying concentrations (0.078-10 mg/mL) were subjected to in vitro α-amylase and dipeptidyl peptidase-4 (DPP-4) inhibitory assay. Molecular docking was performed to study the binding mechanism of active compounds towards α-amylase and DPP-4 enzymes. The antioxidant activity of M. latifolia fractions and compounds were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and ß-carotene bleaching assays. RESULTS: Melicope latifolia chloroform extract showed the highest antidiabetic activity (α-amylase IC50: 1464.32 µg/mL; DPP-4 IC50: 221.58 µg/mL). Fractionation of chloroform extract yielded four major fractions (CF1-CF4) whereby CF3 showed the highest antidiabetic activity (α-amylase IC50: 397.68 µg/mL; DPP-4 IC50: 37.16 µg/mL) and resulted in ß-sitosterol (1), halfordin (2), methyl p-coumarate (3), and protocatechuic acid (4). Isolation of compounds 2-4 from the species and their DPP-4 inhibitory were reported for the first time. Compound 2 showed the highest α-amylase (IC50: 197.53 µM) and ß-carotene (88.48%) inhibition, and formed the highest number of molecular interactions with critical amino acid residues of α-amylase. The highest DPP-4 inhibition was exhibited by compound 3 (IC50: 911.44 µM). DISCUSSION AND CONCLUSIONS: The in vitro and in silico analyses indicated the potential of M. latifolia as an alternative source of α-amylase and DPP-4 inhibitors. Further pharmacological studies on the compounds are recommended.

Identification of Dipeptidyl Peptidase-4 and α-Amylase Inhibitors from Melicope glabra (Blume) T. G. Hartley (Rutaceae) Using Liquid Chromatography Tandem Mass Spectrometry, In Vitro and In Silico Methods.

The present study investigated the antidiabetic properties of the extracts and fractions from leaves and stem bark of M. glabra based on dipeptidyl peptidase-4 (DPP-4) and α-Amylase inhibitory activity assays. The chloroform extract of the leaves was found to be most active towards inhibition of DPP-4 and α-Amylase with IC50 of 169.40 µg/mL and 303.64 µg/mL, respectively. Bioassay-guided fractionation of the leaves' chloroform extract revealed fraction 4 (CF4) as the most active fraction (DPP-4 IC50: 128.35 µg/mL; α-Amylase IC50: 170.19 µg/mL). LC-MS/MS investigation of CF4 led to the identification of trans-decursidinol (1), swermirin (2), methyl 3,4,5-trimethoxycinnamate (3), renifolin (4), 4',5,6,7-tetramethoxy-flavone (5), isorhamnetin (6), quercetagetin-3,4'-dimethyl ether (7), 5,3',4'-trihydroxy-6,7-dimethoxy-flavone (8), and 2-methoxy-5-acetoxy-fruranogermacr-1(10)-en-6-one (9) as the major components. The computational study suggested that (8) and (7) were the most potent DPP-4 and α-Amylase inhibitors based on their lower binding affinities and extensive interactions with critical amino acid residues of the respective enzymes. The binding affinity of (8) with DPP-4 (-8.1 kcal/mol) was comparable to that of sitagliptin (-8.6 kcal/mol) while the binding affinity of (7) with α-Amylase (-8.6 kcal/mol) was better than acarbose (-6.9 kcal/mol). These findings highlight the phytochemical profile and potential antidiabetic compounds from M. glabra that may work as an alternative treatment for diabetes.

Cytotoxic Activity of Christia vespertilionis Root and Leaf Extracts and Fractions against Breast Cancer Cell Lines.

Christia vespertilionis, commonly known as 'Daun Rerama', has recently garnered attention from numerous sources in Malaysia as an alternative treatment. Its herbal decoction was believed to show anti-inflammatory and anti-cancer effects. The present study investigated the cytotoxicity of the extract of root and leaf of C. vespertilionis. The plant parts were successively extracted using the solvent maceration method. The most active extract was further fractionated to afford F1-F8. The cytotoxic effects were determined using MTT assay against human breast carcinoma cell lines (MCF-7 and MDA-MB-231). The total phenolic content (TPC) of the extracts were determined. The antioxidant properties of the extract were also studied using DPPH and ß-carotene bleaching assays. The ethyl acetate root extract demonstrated selective cytotoxicity especially against MDA-MB-231 with the highest TPC and antioxidant properties compared to others (p < 0.05). The TPC and antioxidant results suggest the contribution of phenolic compounds toward its antioxidant strength leading to significant cytotoxicity. F3 showed potent cytotoxic effects while F4 showed better antioxidative strength compared to others (p < 0.05). Qualitative phytochemical screening of the most active fraction, F3, suggested the presence of flavonoids, coumarins and quinones to be responsible toward the cytotoxicity. The study showed the root extracts of C. vespertilionis to possess notable anti-breast cancer effects.

Comparative study of the antidiabetic potential of Paederia foetida twig extracts and compounds from two different locations in Malaysia.

Context: Paederia foetida L. (Rubiaceae) is an edible plant distributed in Asian countries including Malaysia. Fresh leaves have been traditionally used as a remedy for indigestion and diarrhea. Several phytochemical studies of the leaves have been documented, but there are few reports on twigs. Objective: This study investigates the enzyme inhibition of P. foetida twig extracts and compound isolated from them. In addition, in silico molecular docking of scopoletin was investigated. Materials and methods: Plants were obtained from two locations in Malaysia, Johor (PFJ) and Pahang (PFP). Hexane, chloroform and methanol extracts along with isolated compound (scopoletin) were evaluated for their enzyme inhibition activities (10,000-0.000016 µg/mL). The separation and identification of bio-active compounds were carried out using column chromatography and spectroscopic techniques, respectively. In silico molecular docking of scopoletin with receptors (α-amylase and α-glucosidase) was carried out using AutoDock 4.2. Results: The IC50 values of α-amylase and α-glucosidase inhibition activity of PFJ chloroform extract were 9.60 and 245.6 µg/mL, respectively. PFP chloroform extract exhibited α-amylase and α-glucosidase inhibition activity (IC50 = 14.83 and 257.2 µg/mL, respectively). The α-amylase and α-glucosidase inhibitory activity of scopoletin from both locations had IC50 values of 0.052 and 0.057 µM, respectively. Discussion and conclusions: Separation of PFJ chloroform extract afforded scopoletin (1), stigmasterol (2) and γ-sitosterol (3) and the PFP chloroform extract yielded (1), (2), (3) and ergost-5-en-3-ol (4). Scopoletin was isolated from this species for the first time. In silico calculations gave a binding energy between scopoletin and α-amylase of -6.03 kcal/mol.

Cytotoxic constituent of Melicope latifolia (DC.) T. G. Hartley.

An undescribed conjugated sesquiterpene, amelicarin (1), together with nine known compounds (2-10) were isolated for the first time from Melicope latifolia. Their structures were elucidated by extensive NMR spectroscopic and mass spectrometric methods. The conjugated sesquiterpene possesses a unique 6/6/9/4-ring fused tetracyclic skeleton. The proposed biosynthesis pathway of 1 consist of three reactions steps: (1) polyketide formation, (2) cyclisation and (3) addition to form the conjugated sesquiterpenoid as final metabolite. Out of the ten isolated metabolites, amelicarin (1) showed activity against 4 cancerous cell lines namely SK-MEL skin cancer, KB oral cancer, BT-549 breast cancer, and SK-OV-3 ovarian cancer with IC50 values between 15 and 25 µg/mL.

Isolation of antioxidative compounds from Micromelum minutum guided by preparative thin layer chromatography-2,2-diphenyl-1-picrylhydrazyl (PTLC-DPPH) bioautography method.

The application of preparative thin layer chromatography-2,2-diphenyl-1-picrylhydrazyl (PTLC-DPPH) bioautography technique successfully isolated a lignan sesamin (1), two prenylated coumarins (2 and 3) and a marmesin glycosides (4) from Micromelum minutum methanol bark extract. Compounds 2 and 3 were identified as new compounds whereas 1 and 4 were first isolated from Micromelum genus. Structural identification of all compounds were done by detailed spectroscopic analyses and comparison with literature data. Antioxidant capacities of extract, active fraction and compounds were measured based on DPPH free radical savenging activity, oxygen radical absorbance capacity (ORAC) and ß-carotene bleaching. The DPPH activity of methanol extract and its fraction present the IC50 values of 54.3 and 168.9 µg/mL meanwhile the ß-carotene bleaching results were 55.19% and 5.75% respectively. The ORAC measurements of M. minutum extract, compounds 2 and 4 showed potent antioxidant activity with the values of 5123, 5539 and 4031 µmol TE/g respectively.