RECENT ADVANCES IN APPLICATIONS OF ACTIVE CONSTITUENTS OF SELECTED MEDICINAL PLANTS OF DHOFAR, SULTANATE OF OMAN

 The Dhofar region of Oman is extremely opulent in plant biodiversity in comparison to other parts of the country. Most of the cultivated, medicinal and wild plants of the region are available in the mountainous side and hilly areas of Dhofar. The plants produce products from primary metabolism and others from secondary metabolism. On the basis of active constituents plants can be categorized into two groups:1. Medicinal plants and2. Aromatic plants.Over 250 complex chemicals have been recognized and extracted from herbal sources. In this review article, we discuss a selection of medicinal plants of the Dhofar region of Oman which are rich in active constituents and through recent reports discuss the application of the most active constituents. Among the medicinal plants of the Dhofar region, frankincense is also a well-known indicator of the region and has a unique position through its medicinal properties of its oil and gum resin

In vitro antimicrobial activity of frankincense oils from boswellia sacra grown in different locations of the Dhofar region (Oman)

Frankincense essential oils from Boswellia sacra have been commonly used to treat microbial infections from as early as the 11th century. The main feature of the plant is its gum resin, from which it is possible to obtain essential oils. In the present study, we focused on the comparative study of the oils extracted from the resins of three dierent Boswellia sacra cultivars (Najdi, Sahli and Houjri). From each of frankincense resin three successive essential oil samples (Grade 1, Grade 2, Grade 3) were obtained. Houjri gum resin gave the lowest percentage (5%) of total essential oil content but showed the maximum number of volatile components in all three grades. Najdi Grade 2 essential oil showed a minimum inhibitory concentration (MIC) of 52 mg/mL toward relevant pathogens Staphylococcus aureus and Pseudomonas aeruginosa, and samples from Grade 2 of Sahily and Houjiri were particularly active against a dermatological strain Propionibacterium acnes, displaying MIC values of 0.264 and 0.66 mg/mL, respectively. Data obtained from in vitro studies showed that all essential oils had a significant antifungal eect against Candida albicans and Malassezia furfur, showing MIC values ranging from 54.56 to 0.246 mg/mL. This work aims to increase the number of substances available in the fight against pathogens and to combat the phenomenon of antibiotic resistance, encouraging the use of alternative resources, especially in non-clinical settings (farms, food processing, etc.)

In Vitro Antimicrobial Activity of Frankincense Oils from Boswellia sacra Grown in Different Locations of the Dhofar Region (Oman)

Frankincense essential oils from Boswellia sacra have been commonly used to treat microbial infections from as early as the 11th century. The main feature of the plant is its gum resin, from which it is possible to obtain essential oils. In the present study, we focused on the comparative study of the oils extracted from the resins of three different Boswellia sacra cultivars (Najdi, Sahli and Houjri). From each of frankincense resin three successive essential oil samples (Grade 1, Grade 2, Grade 3) were obtained. Houjri gum resin gave the lowest percentage (5%) of total essential oil content but showed the maximum number of volatile components in all three grades. Najdi Grade 2 essential oil showed a minimum inhibitory concentration (MIC) of 52 mg/mL toward relevant pathogens Staphylococcus aureus and Pseudomonas aeruginosa, and samples from Grade 2 of Sahily and Houjiri were particularly active against a dermatological strain Propionibacterium acnes, displaying MIC values of 0.264 and 0.66 mg/mL, respectively. Data obtained from in vitro studies showed that all essential oils had a significant antifungal effect against Candida albicans and Malassezia furfur, showing MIC values ranging from 54.56 to 0.246 mg/mL. This work aims to increase the number of substances available in the fight against pathogens and to combat the phenomenon of antibiotic resistance, encouraging the use of alternative resources, especially in non-clinical settings (farms, food processing, etc.)

Chemical Composition, Antibacterial Activity, and Antibiotic Potentiation of Boswellia sacra Flueck. Oleoresin Extracts from the Dhofar Region of Oman

The emergence of MDR bacterial pathogens has directed antibiotic discovery research towards alternative therapies and traditional medicines. Boswellia sacra oleoresin (frankincense) was used to treat bacterial infections in traditional Arabian and Asian healing systems for at least 1000 years. Despite this, B. sacra extracts have not been rigorously tested for inhibitory activity against gastrointestinal pathogens or bacterial triggers of autoimmune diseases. Solvent extracts were prepared from Boswellia sacra oleoresins obtained from three regions near Salalah, Oman. MIC values were quantified against gastrointestinal pathogens and bacterial triggers of selected autoimmune diseases by disc diffusion and broth dilution methods. The antibacterial activity was also evaluated in combination with conventional antibiotics, and the class of interaction was determined by ΣFIC analysis. Isobolograms were used to determine the optimal ratios for synergistic combinations. Toxicity was evaluated by ALA and HDF cell viability bioassays. The phytochemical composition of the volatile components of all extracts was identified by nontargeted GC-MS headspace analysis. All methanolic extracts inhibited the growth of all of the bacteria tested, although the extracts prepared using Najdi oleoresin were generally more potent than the Sahli and Houjari extracts. Combinations of the methanolic B. sacra extracts and conventional antibiotics were significantly more effective in inhibiting the growth of several bacterial pathogens. In total, there were 38 synergistic and 166 additive combinations. Approximately half of the synergistic combinations contained tetracycline. All B. sacra extracts were nontoxic in the ALA and HDF cell viability assays. Nonbiased GC-MS headspace analysis of the methanolic extracts putatively identified a high diversity of monoterpenoids, with particularly high abundances of α-pinene. The antibacterial activity and lack of toxicity of the B. sacra extracts indicate their potential in the treatment and prevention of gastrointestinal and autoimmune diseases. Furthermore, the extracts potentiated the activity of several conventional antibiotics, indicating that they may contain resistance-modifying compounds

Anti-poliovirus activity of Nerium oleander aqueous extract

Nerium oleander (NO), a member of the Apocynaceae family, is an ornamental plant. In this study, we evaluated the antiviral activity of hot and cold extract of NO against six different viruses such as herpes simplex virus type 1 (HSV-1), polio virus type 1 (Sb-1), vesicular stomatitis virus (VSV), reovirus type-1 (Reo-1), human immunodeficiency virus type-1 (HIV-1), and yellow fever virus (YFV). Interestingly the results of plaque reduction assay demonstrated that both, hot extract and cold extract (breastin) of NO inhibited Sb-1 viral infection. In order to identify the mechanism by which NO exerts its antiviral activity, the virucidal effect, the time of addition and the adsorption assay were carried out. Results demonstrated that NO exerts its effect after infection period, particularly during the first two hours post infection

Characterization of the anticancer properties of monoglycosidic cardenolides isolated from Nerium oleander and Streptocaulon tomentosum

Aim of the study: For identification of the active constituents we investigated the anticancer activity of cardenolides from Streptocaulon tomentosum Wight & Arn. (Asclepiadaceae) and from Nerium oleander L. (Apocynaceae) which are both used against cancer in the traditional medicine in their region of origin. Material, methods and results: The antiproliferative activity of cardenolides isolated from roots of Streptocaulon tomentosum (IC50 < 1–15.3 M after 2 days in MCF7) and of cardenolide containing fractions from the cold aqueous extract of Nerium oleander leaves (“Breastin”, mean IC50 0.85 g/ml in a panel of 36 human tumor cell lines), their influence on the cellular viability and on the cell cycle (block at the G2/Mphase or at the S-phase in tumor cells, respectively) were determined using different cell lines. The murine cell line L929 and normal non-tumor cells were not affected. Bioactivity guided fractionation of Breastin resulted in the isolation of the monoglycosidic cardenolides oleandrine, oleandrigeninsarmentoside, neritaloside, odoroside H, and odoroside A (IC50-values between 0.010 and 0.071 g/ml). Conclusions: The observed anticancer activities of extracts and isolated cardenolides are in agreement with the ethnomedicinal use of Streptocaulon tomentosum and Nerium oleander. The most active anticancer compounds from both species are monoglycosidic cardenolides possessing the 3ˇ,14ˇ-dihydroxy-5ˇ- card-20(22)-enolide structure with or without an acetoxy group at C-16. The results indicate that the cytotoxic effects are induced by the inhibition of the plasma membrane bound Na+/K+-ATPase

Molecular Modes of Action of an Aqueous <i>Nerium oleander</i> Extract in Cancer Cells In Vitro and In Vivo

Cancer drug resistance remains a major obstacle in clinical oncology. As most anticancer drugs are of natural origin, we investigated the anticancer potential of a standardized cold-water leaf extract from Nerium oleander L., termed Breastin. The phytochemical characterization by nuclear magnetic resonance spectroscopy (NMR) and low- and high-resolution mass spectrometry revealed several monoglycosidic cardenolides as major constituents (adynerin, neritaloside, odoroside A, odoroside H, oleandrin, and vanderoside). Breastin inhibited the growth of 14 cell lines from hematopoietic tumors and 5 of 6 carcinomas. Remarkably, the cellular responsiveness of odoroside H and neritaloside was not correlated with all other classical drug resistance mechanisms, i.e., ATP-binding cassette transporters (ABCB1, ABCB5, ABCC1, ABCG2), oncogenes (EGFR, RAS), tumor suppressors (TP53, WT1), and others (GSTP1, HSP90, proliferation rate), in 59 tumor cell lines of the National Cancer Institute (NCI, USA), indicating that Breastin may indeed bypass drug resistance. COMPARE analyses with 153 anticancer agents in 74 tumor cell lines of the Oncotest panel revealed frequent correlations of Breastin with mitosis-inhibiting drugs. Using tubulin-GFP-transfected U2OS cells and confocal microscopy, it was found that the microtubule-disturbing effect of Breastin was comparable to that of the tubulin-depolymerizing drug paclitaxel. This result was verified by a tubulin polymerization assay in vitro and molecular docking in silico. Proteome profiling of 3171 proteins in the NCI panel revealed protein subsets whose expression significantly correlated with cellular responsiveness to odoroside H and neritaloside, indicating that protein expression profiles can be identified to predict the sensitivity or resistance of tumor cells to Breastin constituents. Breastin moderately inhibited breast cancer xenograft tumors in vivo. Remarkably, in contrast to what was observed with paclitaxel monotherapy, the combination of paclitaxel and Breastin prevented tumor relapse, indicating Breastin’s potential for drug combination regimens