BACKGROUND : Antimutagenic activity of plant extracts is important in the discovery of new, effective cancer
preventing agents. There is increasing evidence that cancer and other mutation-related diseases can be prevented by
intake of DNA protective agents. The identification of antimutagenic agents present in plants presents an effective
strategy to inhibit pathogenic processes resulting from exposure to mutagenic and/or carcinogenic substances present
in the environment. There are no reports on the antimutagenic activities of the plant species investigated in this study.
Many mutations related to oxidative stress and DNA damage by reactive oxygen species (ROS) and reactive nitrogen
species (RNS) have been identified in numerous human syndromes. Oxidative DNA damage plays a significant role
in mutagenesis, cancer, aging and other human pathologies. Since oxidative DNA damage plays a role in the
pathogenesis of several chronic degenerative diseases, the decrease of the oxidative stress could be the best
possible strategy for prevention of these diseases. Antioxidant compounds can play a preventative role against
mutation-related diseases, and thus have potential antimutagenic effects.
METHODS : The number of antioxidant compounds present in methanol leaf extracts of 120 plant species was
determined using a combination of Thin Layer Chromatography (TLC) and spraying with 2, 2-diphenyl-1-picrylhydrazyl
(DPPH). The 31 most promising extracts were selected for further assays. The quantitative antioxidant activity was
determined using DPPH free radical scavenging spectrophotometric assay. Total phenolic contents were determined
using the Folin-Ciocalteu colorimetric assay. The mutagenicity of 31 selected extracts was determined in the
Ames test using Salmonella typhimurium strains TA98 and TA100. The antimutagenicity of the plant extracts
against 4-nitroquinoline 1-oxide (4-NQO) was also determined using the Ames test.
METHODS : Of the 120 plant extracts assayed qualitatively, 117 had some antioxidant activity. The selected 31
extracts contained well defined antioxidant compounds. These species had good DPPH free radical antioxidant
activity with EC50 values ranging from 1.20 to 19.06 μg/ml. Some of the plant extracts had higher antioxidant
activity than L-ascorbic acid (vitamin C). The total phenolic contents ranged from 5.17 to 18.65 mg GAE (gallic
acid equivalent)/g plant extract). The total phenolic content of the plant extracts correlated well with the respective
antioxidant activity of the plant extracts. No plant extract with good antioxidant activity had mutagenic activity.
Several extracts had antimutagenic activity. The percentage inhibition of 4-NQO ranged from 0.8 to 77% in
Salmonella typhimurium TA98 and from 0.8 to 99% in strain TA100. There was a direct correlation between the
presence of antioxidant activity and antimutagenic activity of the plant extracts. Although no plant extract had
mutagenic activity on its own, some of the plant extracts enhanced the mutagenicity of 4-NQO, a phenomenon
referred to as comutagenicity.
CONCLUSIONS : Some of the plant extracts investigated in this study had potential antimutagenic activities. The
antimutagenic activities may be associated with the presence of antioxidant polyphenols in the extracts. From
the results plant extracts were identified that were not mutagenic, not cytotoxic and that may be antimutagenic
in the Ames test. For most plant extracts, at the highest concentration used (5 mg/ml), the level of antimutagenicity
was below the recommended 45% to conclude whether plants have good antimutagenic activity. However, in most
screening studies for antimutagenesis, a 20% decrease in the number of revertants must be obtained in order to score
the extract as active. Psoralea pinnata L. had the highest percentage antimutagenicity recorded in this study (76.67 and
99.83% in S. typhimurium TA98 and TA100 respectively) at assayed concentration of 5 mg/ml.
The results indicate that investigating antioxidant activity and the number of antioxidant compounds in plant extracts
could be a viable option in searching for antimutagenic compounds in plants.