Quality of medicinal plants traditionally used in Sudan as affected by ionizing radiation treatments

This investigation was conducted to study the effect of gamma-radiation doses of 5, 10 and 15 KGy on the microbial and chemical quality as well as antioxidant activity of nine medical plants from 8 plant species grown in Sudan. The plant materials were collected from the country-side of Khartoum State as well as from local markets. Plant parts were selected according to their traditional uses as medicinal plants. Irradiation treatment was carried out or dried ground samples using doses of 5,10, 15 KGy from experimental cobalt-60 gamma source. Plants extracts were prepared using 80% methanol. The control and irradiated samples were analyzed for total bacterial count (cfu/g), secondary compounds, tannin content, total phenol, and antioxidant activity. Tannins, flavonoids, glycosides, anthraquinones, saponin and phenols were evaluated through major compounds in extracts. The total bacterial count indicated that the non- irradiated samples of Trigonella foenum-graecum L., Cassia senna (pods), Cassia senna (leaves), Acacia nilotica L., Brassica nigra L. Koch, Lepidium sativum L., Cymbopogon citratus and Hibiscus sabdariffa L. were highly contaminated with bacteria. The sample of Cymbopogon schoenanthus L. showed a lower count of bacteria (9x10'' 3 Cfu/g), which did not exceed the acceptable level. The samples irradiated with 5, 10 and 15 KGy of gamma radiation dose had significantly lower bacterial counts than the non-irradiated control. The highest sensitivity to gamma rays at 5 KGy dose was observed in Trigonella foenum-graecum L. and Acacia nilotica L. while the lowest sensitivity was in Cymbopogon schoenanthus L. At 15 KGy dose Hibiscus sabdariffa L. and Cymbopogon citratus showed complete absence of microorganisms. The highest reduction in tannin content (mg/L catechin) due to irradiation with 15 KGy dose was observed in Cymbopogon citratus, followed by Cymbopogon schoenanthus L., Cassia senna L. leaves Acacia nilotica L. and Hibiscus sabdariffa L.. Irradiation with 15 KGy dose increased the tannin content in Brassica nigra L. Koch, Trigonella foenum-graecum L., Lepidium sativum L. and Cassia senna L. (pods). Irradiation with 15 KGy dose caused slight increase in phenol content in Brassica nigra L. Koch followed by Cassia senna L. (pods) with highest increase observed in Cassia senna L. (leaves) followed by Lepidium sativum L. and Cymbopogon schoenanthus L. Irradiation with 15 KGy dose reduced the phenol content of Trigonella foenum-graecum L., Hibiscus sabdariffa L., Acacia nilotica and Cymbopogon citratus. Irradiation with 15 KGy dose resulted in an insignificant increase in the DPPH radical-scavenging ability of the extracts of lepidium sativum, Cymbopogon Schoenanthus L. and Trigonella foenum-graecum L., compared to the non-irradiated samples. Cassia senna L, pods, cassia senna leaves, Brassica nigra, Hibiscus sabdariffa and Cymbopogon citratus, showed insignificant decrease in the radical-scavenging ability, and also there was no effect on the antioxidant potential of Acacia nilotica L. It appeared that the high dose 15 KGy of gamma irradiation was the most suitable dose for microbial decontamination of the tested plants. Only Cymbopogon citratus and Hibiscus sabdariffa L. achieved commercial sterility (i.e. a total plate counts of counts of <10 cfu/g). However, gamma radiation at a dose greater than 15 KGy may be required to achieve commercial sterility. (Author)