A review of the antioxidant potential of medicinal plant species
Some researchers suggest that two-thirds of the world’s plant species have medicinal value; in particular, many medicinal plants have great antioxidant potential. Antioxidants reduce the oxidative stress in cells and are therefore useful in the treatment of many human diseases, including cancer, cardiovascular diseases and inflammatory diseases. This paper reviews the antioxidant potential of extracts from the stems, roots, bark, leaves, fruits and seeds of several important medicinal species. Synthetic antioxidants such as butylated hydroxytoluene (BHT) and butylated hydroxylanisole (BHA) are currently used as food additives, and many plant species have similar antioxidant potentials as these synthetics. These species include Diospyros abyssinica, Pistacia lentiscus, Geranium sanguineum L., Sargentodoxa cuneata Rehd. Et Wils, Polyalthia cerasoides (Roxb.) Bedd, Crataeva nurvala Buch-Ham., Acacia auriculiformis A. Cunn, Teucrium polium L., Dracocephalum moldavica L., Urtica dioica L., Ficus microcarpa L. fil., Bidens pilosa Linn. Radiata, Leea indica, the Lamiaceae species, Uncaria tomentosa (Willd.) DC, Salvia officinalis L., Momordica Charantia L., Rheum ribes L., and Pelargonium endlicherianum. The literature reveals that these natural antioxidants represent a potentially side effect-free alternative to synthetic antioxidants in the food processing industry and for use in preventive medicine.
 Screening of medicinal plant extracts for antioxidant activity
The methanol extracts of nine medicinal plants traditionally used in Chinese medicine were screened for antioxidant activity versus resveratrol, which has been shown to protect cells from oxidative damage [Toxicol. Lett. 102 (1998) 5]. Most of the plant extracts used in this study inhibited the H2O2-induced apoptosis of Chinese hamster lung fibroblast (V79-4) cells. The extracts of Areca catechu var. dulcissima, Paeonia suffruticosa, Alpinia officinarum, Glycyrrhiza uralensis and Cinnamomun cassia strongly enhanced viability against H2O2-induced oxidative damage in V79-4 cells. Relatively high levels of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were detected in extracts of Areca catechu var. dulcissima, Paeonia suffruticosa and Cinnamomun cassia (IC50 < 6.0 μg/ml). The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) were dose-dependently enhanced in V79-4 cells treated with most of the plant extracts. The extracts of Areca catechu var. dulcissima showed higher antioxidant activity than resveratrol in all experiments. These results suggest that the plant extracts prevent oxidative damage in normal cells probably because of their antioxidant characteristics.
 Screening of 70 medicinal plant extracts for antioxidant capacity and total phenols
The total phenolic content and related total antioxidant capacity of 70 medicinal plant infusions was analyzed. Infusions were prepared in common way in which teas are prepared for human consumption. The total phenolics were measured by Folin–Ciocalteau assay. The total antioxidant capacity was estimated by Ferric Reducing/Antioxidant Power (FRAP) assay. To make practical comparison of relative antioxidant potential of phenolics extracted from selected medicinal plants, the phenol antioxidant coefficient (PAC) was calculated for each infusion. The total phenolic content of medicinal plant infusions ranges from 9 to 2218 mg/L. The FRAP range from 0.06 to 25 mM/L. There was significant linear correlation between total phenolic content and FRAP. According to their antioxidant capacity, 70 medicinal plant extracts can be divided in five groups: (a) very low FRAP (<1 mM/L) n = 9; (b) low FRAP (1–5 mM/L), n = 37; (c) good FRAP (5–10 mM/L), n = 15; (d) high FRAP (10–20 mM/L), n = 8; and (e) very high FRAP (>20 mM/L), n = 1 medicinal plant extract. The PAC was ranging from 1.1 to 3.9 (average 2.4). The best results were obtained for Melissae folium infusions: high phenolic concentration, very high FRAP (>20 mM/L) and PAC > 3. The effect of infusion time and infusion temperature on the phenolic content, FRAP, and free radical scavenging ability was tested. DPPH radical scavenging ability of Melissae folium phenolics was similar to (+)-catechin but not as good as for quercetin. Compared to Trolox and vitamin C, Melissae folium phenolics were more efficient free ABTS radical scavengers. The results indicate that Melissae folium infusions could be an important dietary source of phenolic compounds with high antioxidant capacity comparable with red wine or beverages like tea.
 Screening of North African Medicinal Plant Extracts for Cytotoxic Activity Against Tumor Cell Lines
Aims: The aim of this study was to evaluate the in vitro cytotoxic activity and cellular effects of organic extracts and fractions of four plants; Inula viscosa, Ormenis eiriolepis (Asteraceae), Retama monosperma (Fabaceae) and Marrubium vulgare (Lamiaceae), all of them used in Moroccan traditional medicine.
Methodology: The four plants were extracted using organic solvents and screened on a panel of human cancer cell lines including cell types from both solid and haematological cancer origin as well as non-transformed murine fibroblasts. Cell viability assays were performed with sixteen plant extracts. Sensitive cell lines were then exposed to increasing concentrations of the most efficient extracts in order to calculate IC50 values. Microscopy, flow cytometry and caspase activity assays were then performed in LN229, SW620 and PC-3 cell lines upon treatment to investigate the cell morphology, cell cycle distribution and cell death.
Results: cell viability assays reveals that at least one extract from each plant was able to exert cytotoxic activity against the majority of cell lines tested, the IC50 values of the active extracts were in most cases ≤ 30 µg/ml. the study of the cellular effects of the most active extracts on LN229, SW620 and PC-3 cell lines shows their ability to promote cell cycle arrest and cell death. The data obtained herein support strongly the use of these plants by traditional healers for the treatment of cancer patients and could have some scientific support indicating the presence of bioactive compounds.
Conclusion: The reported biological activity of these four medicinal plants used in traditional Moroccan medicine provides a starting point for forthcoming studies to determine the molecular basis of their activity and to identify the chemical compounds within the most active extracts responsible for their antitumoral effects.
 Inhibitory Effect of Selected Medicinal Plant Extracts on Phytopathogenic Fungus Fusarium oxysporum (Nectriaceae) Schlecht. Emend. Snyder and Hansen
Aims: The study was aimed to screen antifungal activity of some medicinal plant extracts against F. oxysporum by screening fungistatic, fungicidal activities and minimum inhibitory dilution (MID).
Study Design: All the data were subjected to analysis of variance followed by mean separation through Duncan’s multiple range tests using computer software.
Place and Duration of Study: Faculty of Agricultural Sciences, Sabaragamuwa University of Sri Lanka between June 2012 and May 2013.
Methodology: In vitro studies were carried out to test the antifungal activity of 6 plant extracts; Oxalis corniculata L. (creeping wood sorrel), Ocimum gratissimum L. (wild basil), Tithonia diversifolia (Hemsl.) A.Gray (wild sunflower), Azadirachta indica A.Juss. (neem), Kaempferia galangal L.(aromatic ginger) and Zingiber officinale Roscoe (ginger). All plant extract were screened for their fungistatic, fungicidal activities and minimum inhibitory dilution (MID) against F. oxysporum.
Results: Results showed that radial growth of F. oxysporum was significantly impaired (P = .05) by all extracts except wild sunflower and creeping wood sorrel. F. oxysporum differed in their reaction to the different extracts but on the whole, growth inhibition increased with the concentration of each extract. At 25 %, the most active extracts were aromatic ginger, wild basil and neem, which are shows inhibition values of 91%, 89% and 83% for F. oxysporum respectively. The minimal inhibitory dilution (MID) were 3.125 % (v/v) for aromatic ginger and wild basil and 6.25% (v/v) for ginger. Out of six plants extract screened, wild basil, aromatic ginger and neem showed more than 80% fungal inhibition after 6 hour immersion and other extracts could not exceed 60% inhibition after any exposure time.
Conclusion: The study revealed that methanol crude extract of aromatic ginger, wild basil and neem exhibit strong fungistatic and fungicidal activities against F. oxysporum, whereas aromatic ginger and wild basil could be used as an effective antifungal agent.
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 Lee, S.E., Hwang, H.J., Ha, J.S., Jeong, H.S. and Kim, J.H., 2003. Screening of medicinal plant extracts for antioxidant activity. Life sciences, 73(2), pp.167-179.
 Katalinic, V., Milos, M., Kulisic, T. and Jukic, M., 2006. Screening of 70 medicinal plant extracts for antioxidant capacity and total phenols. Food chemistry, 94(4), pp.550-557.
 Belayachi, L., Aceves-Luquero, C., Merghoub, N., Bakri, Y., de Mattos, S.F., Amzazi, S. and Villalonga, P., 2013. Screening of North African medicinal plant extracts for cytotoxic activity against tumor cell lines. European Journal of Medicinal Plants, pp.310-332.
 Dissanayake, M.L.M.C., 2014. Inhibitory effect of selected medicinal plant extracts on phytopathogenic fungus Fusarium oxysporum (Nectriaceae) Schlecht. Emend. Snyder and Hansen. Annual Research & Review in Biology, pp.133-142.