Rohaya Ahmad

Malaysianol A, a new trimer resveratrol oligomer from the stem bark of Dryobalanops aromatica

A new resveratrol trimer, malaysianol A (1), five known resveratrol oligomers: laevifonol (2), ampelopsin E (3), α-viniferin (4), ε-viniferin (5), diptoindonesin A (6), and bergenin (7) have been isolated from the acetone extract of the stem bark of Dryobalanops aromatica by combination of vacuum and radial chromatography techniques. Their structures were established on the basis of their spectroscopic evidence and comparison with the published data. The cytotoxic activity of the compounds was tested against several cell lines in which compound 4 was found to inhibit strongly the growth of HL-60 cell line.

Antioxidant Activity of Hispidin Oligomers from Medicinal Fungi: A DFT Study

Hispidin oligomers are styrylpyrone pigments isolated from the medicinal fungi Inonotus xeranticus and Phellinus linteus. They exhibit diverse biological activities and strong free radical scavenging activity. To rationalize the antioxidant activity of a series of four hispidin oligomers and determine the favored mechanism involved in free radical scavenging, DFT calculations were carried out at the B3P86/6-31+G (d, p) level of theory in gas and solvent. The results showed that bond dissociation enthalpies of OH groups of hispidin oligomers (ArOH) and spin density delocalization of related radicals (ArO•) are the appropriate parameters to clarify the differences between the observed antioxidant activities for the four oligomers. The effect of the number of hydroxyl groups and presence of a catechol moiety conjugated to a double bond on the antioxidant activity were determined. Thermodynamic and kinetic studies showed that the PC-ET mechanism is the main mechanism involved in free radical scavenging. The spin density distribution over phenoxyl radicals allows a better understanding of the hispidin oligomers formation.

Triterpenoid saponins from Hedyotis nudicaulis

Abstract Three new triterpenoid saponins, nudicaucins A, B and C and a known saponin guaiacin D have been isolated from the n-butanol extract of Hedyotis nudicaulis. The structures of nudicaucins A, B and C were elucidated to be β- d -glucopyranosyl 3-O-[β- d -galactopyranosyl (1 → 3)α- l -arabinopyranosyl]-30-norolean-12,20(29)-dien-28- oate , β- d -glucopyranosyl 3-O-[β- d -galactopyranosyl (1 → 3)α- l -arabinopyranosyl]oleanoate and β- d -glucopyranosyl 3-O- [α- l -rhamnopyranosyl (1 → 2)α- l -arabinopyranosyl (3 → 1)β- d -glucopyranosyl]- oleanoate , respectively, on the basis of NMR spectroscopic analysis and comparison of the spectral data with those of known saponins.

Rauniticine-allo-Oxindole B and Rauniticinic-allo Acid B, New Heteroyohimbine-Type Oxindole Alkaloids from the Stems of Malaysian Uncaria longiflora var. pteropoda

Two new heteroyohimbine-type oxindole alkaloids, rauniticine-allo-oxindole B and rauniticinic-allo acid B, have been successfully isolated from the stems extract of Malaysian Uncaria longiflora var. pteropoda. The structures of the two new alkaloids were determined by spectroscopic analysis.

Chemical constituents of malaysian U. cordata var. ferruginea and their in Vitro α-glucosidase inhibitory activities

Continuing our interest in the Uncaria genus, the phytochemistry and the in-vitro α-glucosidase inhibitory activities of Malaysian Uncaria cordata var. ferruginea were investigated. The phytochemical study of this plant, which employed various chromatographic techniques including recycling preparative HPLC, led to the isolation of ten compounds with diverse structures comprising three phenolic acids, two coumarins, three flavonoids, a terpene and an iridoid glycoside. These constituents were identified as 2-hydroxybenzoic acid or salicylic acid (1), 2,4-dihydroxybenzoic acid (2), 3,4-dihydroxybenzoic acid (3), scopoletin or 7-hydroxy-6-methoxy-coumarin (4), 3,4-dihydroxy-7-methoxycoumarin (5), quercetin (6), kaempferol (7), taxifolin (8), loganin (9) and β-sitosterol (10). Structure elucidation of the compounds was accomplished with the aid of 1D and 2D Nuclear Magnetic Resonance (NMR) spectral data and Ultraviolet-Visible (UV-Vis), Fourier Transform Infrared (FTIR) spectroscopy and mass spectrometry (MS). In the α-glucosidase inhibitory assay, the crude methanolic extract of the stems of the plant and its acetone fraction exhibited strong α-glucosidase inhibition activity of 87.7% and 89.2%, respectively, while its DCM fraction exhibited only moderate inhibition (75.3%) at a concentration of 1 mg/mL. The IC50 values of both fractions were found to be significantly lower than the standard acarbose suggesting the presence of potential α-glucosidase inhibitors. Selected compounds isolated from the active fractions were then subjected to α-glucosidase assay in which 2,4-dihydroxybenzoic acid and quercetin showed strong inhibitory effects against the enzyme with IC50 values of 549 and 556 μg/mL compared to acarbose (IC50 580 μg/mL) while loganin and scopoletin only showed weak α-glucosidase inhibition of 44.9% and 34.5%, respectively. This is the first report of the isolation of 2-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid and loganin from the genus and the first report of the α-glucosidase inhibitory potential of 2,4-dihydroxybenzoic acid.

Evaluation of antioxidant potential of Artocarpus heterophyllus L. J33 variety fruit waste from different extraction methods and identification of phenolic constituents by LCMS

Artocarpus heterophyllus J33 (AhJ33) fruit is a popular and valuable jackfruit variety in Malaysia. For export, the pulp has to be separated from the skin which is usually discarded. Hence, the conversion of the fruit waste to food products with economic value needs to be explored utilizing the waste to wealth concept. This paper reports the evaluation of antioxidant potential of AhJ33 fruit waste (rind and rachis) extracts from three different extraction methods (maceration, percolation and Soxhlet). The antioxidant potential was assessed by DPPH radical scavenging, FRAP and β-carotene bleaching assays. The total phenolic and total flavonoid contents were estimated by TPC and the TFC assays. For both rind and rachis, the maceration technique yielded extracts with the strongest antioxidant activities which correlated with the highest TPC and TFC values. TOF LCMS analyses identified two phenolic acids as the major constituents responsible for the antioxidant activity of the active extracts.

Optimization of ball milling parameters to produce Centella asiatica herbal nanopowders

Nanopowders of Centella asiatica was produced using planetary ball mill by varying milling parameters such as milling time, mass concentration, and bead amount. Particle size analysis employing photon correlation spectroscopy was carried out to record the effect of milling parameters on the particle size produced. The morphology of milled powders was also analyzed using a field emission scanning electron microscope. The bioactive component, asiatic acid, was extracted from various sizes of C. asiatica powders, and its extraction yield at different powder size was calculated by high-performance liquid chromatography. Optimization of milling parameters was found to be a crucial step in determining the content of asiatic acid extracted. In this study, the highest amount of asiatic acid extracted was 25.4 mg/g, obtained at moderate conditions of the following milling parameters: 4 h of milling time, 1.2% (w/v) concentration of powder, and 25 g of bead load.

Inhibition of Free Radical and Neuroprotective Effect of Four Varieties of Ficus deltoidea

Oxidative stress and the implications have been highlighted in the pathogenesis of many neurodegenerative disorder of the brain including Alzheimer’s disease. Nowadays, the interests in the protective role of several plants extracts are growing up. Plants antioxidants ability includes the inhibition of reactive oxygen species (ROS) overproduction and up-regulation of endogenous antioxidant defences. In this study, neuroblastoma cell line, SH-SY5Y was used to determine the neuroprotective effect of the leaves and figs of aqueous extract of four varieties of Ficus deltoidea namely var kunstleri, var angustifolia, var deltoidea, and var intermedia. The study showed the positive interaction between the inhibition of free radical with the neuroprotective effect against hydrogen peroxide (H2O2)-induced in SH-SY5Y cells.

Radical scavenging and neurotoxicity of four varieties of Ficus deltoidea

Ficus deltoidea or locally known as ‘Mas Cotek’ is a very common herb found throughout the tropics is available in many varieties. In Malaysia, traditional practitioners use this plant in herbal remedies to treat several illnesses like headache, hypertension, and hyperglycemia which may be related to antioxidant properties of the plant. The first objective of the study was to evaluate antioxidant properties of aqueous extracts of four varieties of Ficus deltoidea namely var angustifolia, deltoidea, intermedia, and kunstleri in order to identify which variety possess the highest antioxidant potential. In this study, the antioxidant of aqueous extract of the leaves and fruits of the four varieties of Ficus deltoidea were evaluated by their DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity. In addition, total phenolic content (TPC) of the aqueous extracts were also determined by the Folin-Ciocalteu method. The TPC value of var intermedia was very good both for the leaves and fruits (86.52 and 96.58 mg GAE/100 g extract respectively) compared to other varieties. In the DPPH assay, var deltoidea showed the highest radical scavenging activity both for the leaves and fruits (82.04% and 71.43% respectively) compared to other varieties. The second objective was to study the neurotoxicity. In this study, neuroblastoma cell line, SH-SY5Y was used to determine the neurotoxicity of aqueous extracts of four varieties of Ficus deltoidea. Cell viability was assessed using MTS assay. Results showed that the aqueous extracts of four varieties of Ficus deltoidea were not toxic within the tested concentration range from 1 ng/ml to 1 mg/ml. The study also showed that the aqueous extracts could protect neuron cells and suggested that the varieties possess potential neuroprotective effects.

Green Extraction: Enhanced Extraction Yield of Asiatic Acid from Centella asiatica (L.) Nanopowders

Nanopowders of Centella asiatica (L.) were produced using planetary ball mill in order to investigate the differences of water extraction yield of asiatic acid as compared to micropowders of Centella asiatica. Effect of extraction time (20–60 min) on extraction yield of asiatic acid from Centella asiatica was examined. Results showed that water extraction of asiatic acid using Centella asiatica nanopowders exhibits was almost 50% higher extraction yield with 7.09 mg/g as compared to the micropowders of Centella asiatica. It was concluded that nanopowders contributed in enhancing water extraction yield of asiatic acid as compared to micropowders. Thereby utilizing nanopowders in water extraction could improve the extraction of asiatic acid via clean, eco-friendly, and less expensive process.