Khalid Hamid Musa

A novel high throughput method based on the DPPH dry reagent array for determination of antioxidant activity.

A stable chromogenic radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) is commonly used for the determination of antioxidant activity. In this paper, DPPH was dried into 96 well microplate to produce DPPH dry reagent array plate, based on which the highly sensitive and high throughput determination of antioxidant activities was achieved. The spectrophotometric characterization of the microplate containing dried or fresh DPPH free radicals was reported. The response of the DPPH dry reagent array towards different standard antioxidants was studied. The reaction for DPPH in fresh or dry reagent array with Trolox was reported and compared. The DPPH dry reagent array was used to study the antioxidant activity of banana, green tea, pink guava, and honeydew and the results were compared to the samples reacted with freshly prepared DPPH. The proposed method is comparable to the classical DPPH method, more convenient, simple to operate with minimal solvent required and excellent sensitivity.

Determination of DPPH free radical scavenging activity: Application of artificial neural networks

A new computational approach for the determination of 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity (DPPH-RSA) in food is reported, based on the concept of machine learning. Trolox standard was mix with DPPH at different concentrations to produce different colors from purple to yellow. Artificial neural network (ANN) was trained on a typical set of images of the DPPH radical reacting with different levels of Trolox. This allowed the neural network to classify future images of any sample into the correct class of RSA level. The ANN was then able to determine the DPPH-RSA of cinnamon, clove, mung bean, red bean, red rice, brown rice, black rice and tea extract and the results were compared with data obtained using a spectrophotometer. The application of ANN correlated well to the spectrophotometric classical procedure and thus do not require the use of spectrophotometer, and it could be used to obtain semi-quantitative results of DPPH-RSA.

Antioxidant properties of ginger (Kaempferia angustifolia Rosc.) and its chemical markers

ABSTRACT The nutritional value of the rhizomes of Kaempferia angustifolia was measured through the antioxidant properties of various extracts and the determination of the bioactive compounds. The chloroform and methanol extracts of the rhizomes of Kaempferia angustifolia showed strong free radical scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) with values of 615.92 mg Trolox equivalent (TE)/g each. The methanol extract also exhibited the strongest antioxidant properties in the azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) assay with a value of 38.87 mg TE/g. The hexane extract gave the strongest reducing ability in cupric reducing antioxidant capacity (CUPRAC) assay with a value of 901.76 mg TE/g, whilst the ethyl acetate extract exhibited the strongest reducing ability against ferric reducing antioxidant power (FRAP) with a value of 342.23 mg TE/g. Column chromatographic separation on the rhizomes of Kaempferia angustifolia afforded boesenboxide (1), crotepoxide (2), 2ˊ-hydroxy-4,4ˊ,6ˊ-trimethoxychalcone (3), kaempfolienol (4), and zeylenol (5), which were elucidated by spectroscopic methods. Kaempfolienol (4) was the strongest free radical agent against DPPH with a value of 443.92 mg TE/g, whilst 2ˊ-hydroxy-4,4ˊ,6ˊ-trimethoxychalcone (3) exhibited the strongest antioxidant properties with values of 42.23, 1497.22, and 781.53 mg TE/g against ABTS, CUPRAC, and FRAP assays, respectively.

Measurement of Antioxidant Activity and Structural Elucidation of Chemical Constituents from Aglaia oligophylla Miq.

Aglaia oligophylla Miq. is a shrub of approximately 25 meters tall under the Meliaceae family which possess distinct pharmacological properties including insecticides, anti-inflammatory and anticancer. The purpose of this study is to evaluate the antioxidant capacity of the trunks and stem of Aglaia oligophylla plant extracts and to isolate their chemical constituents. The antioxidant activity was evaluated as the reducing antioxidant capacity includes of cupric reducing antioxidant capacity (CUPRAC) and ferric reducing antioxidant power (FRAP) assays. In CUPRAC assay, ethyl acetate extract of the trunks part exhibited the strongest reducing capacity with the value of 1543 mg Trolox equivalent (TE)/g and for the stem part, methanol extract showed the strongest reducing antioxidant capacity with the value of 1059 mg TE/g. In FRAP assay, the methanol extracts of both trunks and stem of the plant showed the strongest reducing power with the values of 1269 mg TE/g and 1084 mg TE/g respectively. Repeated column chromatographic separation on chloroform extract of the trunks part afforded one triterpenes which was suggested to be stigmasterol (1) whilst the separation on methanol extract of the trunks obtained a triterpene, β-sitosterol (2). In the stem of A. oligophylla, the column chromatographic separation on petroleum ether extract afforded a new triterpene, namely oligophyllic acid (3) while the separation on chloroform and ethyl acetate extracts gave compound 2. All the chemical constituents were elucidated by comparison with literature review reported previously. Based on the value of CUPRAC and FRAP antioxidant assays of the plant extracts, A. oligophylla, shows great potential for the possibility of discovery and development of health promoting supplement from the extracts and chemical constituents.

Study of Antioxidant and Anti-Inflammatory Crude Methanol Extract and Fractions of Acacia seyal Gum

Acacia seyal gum (ASG) is a dried exudate from tropical plants in the family Leguminosae. It has been used in the medication of eczema, inflammation, renal failure, and hypertension in folk medicine. This study presents methanol crude extracts (MCE) and different fractions of ASG in the form of raw (ASG) and commercial type Prebio-T, (PTC) using different solvents. Evaluations were performed to observe the biological activities of the extracts and fractions with certain bioassays procedure of anti-inflammatory, total phenolic content (TPC) and radical scavenging activity (DPPH). The only MCE was assessed against inflammatory reaction using carrageenan paw oedema (in-vivo). However, the antioxidant activities of MCE and its fractions were evaluated. As a result, the highest amount of TPC was observed in the Prebio-T, with an average of 694.68 ± 3.60 mgTE/100 g DW, compared to only 155.78 ± 2.58 mg TE/100 g DW for ASG Crude Extract. The highest DPPH value was seen in methanol fraction (MF) was 235.34 ± 1.57 mg TE/100 g DW for Prebio-T, compared to ASG without any significant differences (p ≤ 0.05). Both MCE of ASG and Prebio-T at 150 mg/kg dosage developed a mean and maximum percentage inhibition of 23.63% and 23.54% respectively, during the 24h observation of the acute inflammatory test. The chemical composition of the 57 phenolic compounds in methanol crude extract (MCE), and its active fractions were detected using GC-MS/MS. The major constituents in the ASG and Prebio-T MCE were iso vitamin C (42.37%), crypton (5.86%), hydroquinone (4.86%), triacetic acid lactone (2.67%), 2,4-Di-tert-butyl phenol (2.67%), cyanidin cation (2.05%), apigenin 7-glucoside (1.9%), benzoic acid (1.83%), (+)-α-tocopherol (1.58%), methyl catechol (1.42%), and 2,6-dimethylol-pcresol (2.16%). The PBT methanolic crude extract (MCE) was found to be the most potent inhibitor of oedema formation by inducing a maximum inhibitory effect of 23.54% at the 300 mg/kg dose, during 24h post-carrageenan injection. Both PBT and ASG methanolic crude extracts showed good anti-inflammatory activities at the same dose (300 mg/kg). The results of these studies support the potential use of ASG for treating inflammation.

Determination of antioxidant activities, total phenolic and flavanoid contents in Bougainvillea glabra bracts at various methanol concentrations

The Bougainvillea glabra bract was extracted using three ratios of methanolic solvents at 50%, 70% and 100%. In this study, the methanolic extracts of B. glabra bract were evaluated for antioxidant properties and quantification of phenolics and flavanoids. Methanol at 100% was the highest extraction efficiency among three other methanolic with yield value of 38%. The content of phenolics and flavonoids of B. glabra bracts in methanol 100% were 63.92±0.90 GAE mg/100g and 249.53±26.20 QE mg/100g respectively. The antioxidant activity was measured using three different bioassays namely, DPPH, ABTS and FRAP. The results were expressed as mg Trolox equivalent per 100 g where Trolox is a vitamin E analog. Among these methanol extracts, highest antioxidant capacity was observed in the pure methanol concentration. Positive correlation was observed in B. glabra bract between DPPH assay and TPC, r2=1.00. The methanol extract at 100% was rich in polyphenolics, which indicating that the B. glabra bract has the potent...

Color and Antioxidant Changes in Various Natural Rubber Processes

Fresh field natural rubber was coagulated by acetic acid, soaked in water at room temperature (WRT) or 70°C (W70) for 1 hr, and then dried in an oven at 40°C. Non-soaked natural rubber samples (NoW) served as a control. Two grades of natural rubber, namely air-dry sheet (ADS) and ribbed smoked sheet No.3 (RSS3) derived from the same latex, were also investigated. All dry rubber samples were characterized with Lovibond colorimeter according to ASTM D3157, as well as with a HunterLab spectrophotometer. Furthermore, all the dry rubber samples were dissolved in a chloroform:methanol mixture (4:1 v:v). The rubber was then precipitated out of the solution with methanol, and the remaining solution was quantitatively analyzed for total phenolic content (TPC). The plasticity retention index (PRI) was determined for all the dried rubber samples according to ASTM D3194. It was found that WRT, W70 and ADS were similar in lightness L*, while RSS3 had the lowest L*. W70 had the lowest redness a*, which increased in the order WRT, NoW, RSS3 and ADS. W70 also had the lowest yellowness b*, which increased in the order RSS3, NoW and WRT and ADS. Moreover, TPC was the lowest for the W70 sample, increasing in the order ADS, WRT, NoW and RSS3. The PRI was highest for W70, and decreased in the order WRT, RSS3, NoW and ADS. All of the PRI values observed were comparatively high relative to blocked standard Thai rubber 20 (STR20).