Azman Abd Samad

Cytotoxic Activities against Breast Cancer Cells of Local Justicia gendarussa Crude Extracts

Justicia gendarussa methanolic leaf extracts from five different locations in the Southern region of Peninsular Malaysia and two flavonoids, kaempferol and naringenin, were tested for cytotoxic activity. Kaempferol and naringenin were two flavonoids detected in leaf extracts using gas chromatography-flame ionization detection (GC-FID). The results indicated that highest concentrations of kaempferol and naringenin were detected in leaves extracted from Mersing with 1591.80 mg/kg and 444.35 mg/kg, respectively. Positive correlations were observed between kaempferol and naringenin concentrations in all leaf extracts analysed with the Pearson method. The effects of kaempferol and naringenin from leaf extracts were examined on breast cancer cell lines (MDA-MB-231 and MDA-MB-468) using MTT assay. Leaf extract from Mersing showed high cytotoxicity against MDA-MB-468 and MDA-MB-231 with IC50 values of 23 μg/mL and 40 μg/mL, respectively, compared to other leaf extracts. Kaempferol possessed high cytotoxicity against MDA-MB-468 and MDA-MB-231 with IC50 values of 23 μg/mL and 34 μg/mL, respectively. These findings suggest that the presence of kaempferol in Mersing leaf extract contributed to high cytotoxicity of both MDA-MB-231 and MDA-MB-468 cancer cell lines.

Improvement of efficient in vitro regeneration potential of mature callus induced from Malaysian upland rice seed (Oryza sativa cv. Panderas).

A new and rapid protocol for optimum callus production and complete plant regeneration has been assessed in Malaysian upland rice (Oryza sativa) cv. Panderas. The effect of plant growth regulator (PGR) on the regeneration frequency of Malaysian upland rice (cv. Panderas) was investigated. Mature seeds were used as a starting material for callus induction experiment using various concentrations of 2,4-D and NAA. Optimal callus induction frequency at 90% was obtained on MS media containing 2,4-D (3 mg L−1) and NAA (2 mg L−1) after 6 weeks while no significant difference was seen on tryptophan and glutamine parameters. Embryogenic callus was recorded as compact, globular and light yellowish in color. The embryogenic callus morphology was further confirmed with scanning electron microscopy (SEM) analysis. For regeneration, induced calli were treated with various concentrations of Kin (0.5–1.5 mg L−1), BAP, NAA and 0.5 mg L−1 of TDZ. The result showed that the maximum regeneration frequency (100%) was achieved on MS medium containing BAP (0.5 mg L−1), Kin (1.5 mg L−1), NAA (0.5 mg L−1) and TDZ (0.5 mg L−1) within four weeks. Developed shoots were successfully rooted on half strength MS free hormone medium and later transferred into a pot containing soil for acclimatization. This cutting-edge finding is unique over the other existing publishable data due to the good regeneration response by producing a large number of shoots.

Physical and antioxidative responses of Orthosiphon stamineus towards various copper and lead concentrations

Abstract Plants normally change their physiological and biochemical properties when exposed to heavy metal stress. We investigated the response of Orthosiphon stamineus towards different concentrations of Pb (0, 2, 5, 8 mg/L) and Cu (1, 2, 4, 5 mg/L). Heavy metals left in soil, plant physical characteristics, and the level of antioxidants in O. stamineus were determined. Our results showed that the tested Pb concentrations did not significantly affect stem elongation, but at 2 mg/L, Pb increased the leaf growth. Pb at 5 and 8 mg/L increased the total plant biomass. In contrast, 5 mg/L Cu treatment affected stem elongation and the root length of O. stamineus. The concentrations of Pb and Cu in soil were significantly reduced after the plants were harvested. Biochemically, 5 mg/L Pb had significantly increased the activity of catalase, while Cu at 5 mg/L significantly reduced the activity of superoxide dismutase and ascorbate peroxidase. Total flavonoid content increased in Pb-treated plants, but the total phenolics content decreased. Cu treatment at 2 mg/L, on the other hand increased the total phenolics content. Our results demonstrated that O. stamineus adapt to metal stress via physical changes, and scavenge oxygen radicals through enzymatic and non-enzymatic antioxidant productions.

Molecular cloning and characterization of a cDNA encoding a polyketide synthase from Melastoma decemfidum

A famous plant polyketide synthase (PKS) is a chalcone synthase (CHS), which catalyzes the formation of naringenin chalcone, a limiting factor for flavonoid biosynthesis. Flavonoids such as naringenin and kaempferol-3-O-(2″,6″-di-O-p-trans-coumaroyl glucoside) have been identified from the flower extracts of Melastoma decemfidum RoxB. Therefore, a study was conducted to clone and characterize the pks gene from M. decemfidum. A newly isolated full-length cDNA containing the pks sequence (designated MdCHS; GenBank accession No. KF234569) was found to harbour a 1,355-bp open reading frame encoding 392 amino acids. The deduced MdCHS protein, which had a predicted molecular weight of approximately 42.6 kDa, exhibited 89% sequence identity to CHS from Anthurium andraeanum (GenBank accession No. AY232492) and 91% to those from Camellia sinensis (D26594) and Camellia chekiangoleosa (ADW11243). Southern blot analysis indicated that at least five pks genes are present in M. decemfidum. Additionally, transcription analysis revealed that pks gene expression was higher in roots than in other tissues (shoots, leaves, stems, flower buds and flowers). In conclusion, the characterization and cloning of the MdCHS gene further elucidates its role in flavonoid biosynthesis.