Extracts of plants from the Malaysian rainforest and other fragile habitats are being researched intensively for identification of beneficial biological actions, with assessment of antioxidant behavior being a common component of such assessments. A number of tests for antioxidant behavior are used, with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reduction activity potential (FRAP) assays often being used in parallel, and also with measurement of total phenolics content (TPC) as a surrogate marker for antioxidant capacity. The present study investigated the possible redundancy in using all three assays to determine antioxidant capacity in 92 extracts obtained from 27 plants from the Malaysian rainforest. The results demonstrated that the assays displayed a high (R ≥ 0.82) and significant (P < 0.0001) correlation with one another, indicating a high level of redundancy if all three assays are used in parallel. This appears to be a waste of potentially valuable plant extracts. Because of problems with the FRAP assay relating to color interference and variable rates of reaction point, the DPPH assay is the preferred assay in preliminary screening of extracts of plants from the Malaysian rainforest.

Context: Arsenic, a toxic metalloid with major health concerns, elicits upregulation of heat shock protein 70 (HSP70) in rat hepatoma FGC4 cells, together with evidence of detachment of viable cells from the growth substratum. Objective: To determine if this cell detachment was linked to anoikis, and the impact of this on measurement of HSP70 expression. Materials and methods: FGC4 cells were exposed to sodium arsenite, and detached and attached cells were taken for assessment of cell viability, activation of procaspase-3, and expression of HSP70. Results: Exposure to sodium arsenite led to loss of viable cells from the substratum, associated with apoptosis in detached, but not attached, cells. Upregulation of HSP70 of a similar magnitude was demonstrated in both cell populations. Exposure of cells to cadmium chloride, a toxic metal, also of major environmental concern and believed to act by an oxidative stress mechanism, produced very little release of viable cells from the culture substratum, was not associated with apoptosis, but did elicit a modest upregulation of HSP70 in both cell populations. Discussion: Exposure of FGC4 cells to sodium arsenite elicits anoikis, a form of anchorage-dependent apoptosis, and assessment of the level of HSP70 upregulation in such cells should take account of the detached cell population. Further, the data suggest that this phenomenon is selective to sodium arsenite, rather than to another toxic element that shares a similar mechanism of toxicity.

The O-dealkylation of 7-alkoxycoumarins is widely used as an assay to characterize cytochrome P450 (CYP) activity. These substrates can also undergo oxidative attack at additional sites on the coum...