Ahmed Al-Rawahi

Fruitful Decade for Antileishmanial Compounds from 2002 to Late 2011

2011 Hidayat Hussain,*,† Ahmed Al-Harrasi,*,† Ahmed Al-Rawahi,† Ivan R. Green,‡ and Simon Gibbons* †UoN Chair of Oman’s Medicinal Plants and Marine Natural Products, University of Nizwa, P.O. Box 33, Birkat Al Mauz, Nizwa 616, Sultanate of Oman ‡Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland, Stellenbosch 7600, South Africa Department of Pharmaceutical and Biological Chemistry, UCL School of Pharmacy, London WC1N 1AX, United Kingdom

Bacterial endophyte Sphingomonas sp. LK11 produces gibberellins and IAA and promotes tomato plant growth

Plant growth promoting endophytic bacteria have been identified as potential growth regulators of crops. Endophytic bacterium, Sphingomonas sp. LK11, was isolated from the leaves of Tephrosia apollinea. The pure culture of Sphingomonas sp. LK11 was subjected to advance chromatographic and spectroscopic techniques to extract and isolate gibberellins (GAs). Deuterated standards of [17, 17-2H2]-GA4, [17, 17-2H2]-GA9 and [17, 17-2H2]-GA20 were used to quantify the bacterial GAs. The analysis of the culture broth of Sphingomonas sp. LK11 revealed the existence of physiologically active gibberellins (GA4: 2.97 ± 0.11 ng/ml) and inactive GA9 (0.98 ± 0.15 ng/ml) and GA20 (2.41 ± 0.23). The endophyte also produced indole acetic acid (11.23 ± 0.93 μM/ml). Tomato plants inoculated with endophytic Sphingomonas sp. LK11 showed significantly increased growth attributes (shoot length, chlorophyll contents, shoot, and root dry weights) compared to the control. This indicated that such phyto-hormones-producing strains could help in increasing crop growth.

Endophytic fungi: resource for gibberellins and crop abiotic stress resistance

Abstract The beneficial effects of endophytes on plant growth are important for agricultural ecosystems because they reduce the need for fertilizers and decrease soil and water pollution while compensating for environmental perturbations. Endophytic fungi are a novel source of bioactive secondary metabolites; moreover, recently they have been found to produce physiologically active gibberellins as well. The symbiosis of gibberellins producing endophytic fungi with crops can be a promising strategy to overcome the adverse effects of abiotic stresses. The association of such endophytes has not only increased plant biomass but also ameliorated plant-growth during extreme environmental conditions. Endophytic fungi represent a trove of unexplored biodiversity and a frequently overlooked component of crop ecology. The present review describes the role of gibberellins producing endophytic fungi, suggests putative mechanisms involved in plant endophyte stress interactions and discusses future prospects in this field.

Endophytic Fungi from Frankincense Tree Improves Host Growth and Produces Extracellular Enzymes and Indole Acetic Acid

Boswellia sacra, an economically important frankincense-producing tree found in the desert woodlands of Oman, is least known for its endophytic fungal diversity and the potential of these fungi to produce extracellular enzymes and auxins. We isolated various fungal endophytes belonging to Eurotiales (11.8%), Chaetomiaceae (17.6%), Incertae sadis (29.5%), Aureobasidiaceae (17.6%), Nectriaceae (5.9%) and Sporomiaceae (17.6%) from the phylloplane (leaf) and caulosphere (stem) of the tree. Endophytes were identified using genomic DNA extraction, PCR amplification and sequencing the internal transcribed spacer regions, whereas a detailed phylogenetic analysis of the same gene fragment was made with homologous sequences. The endophytic colonization rate was significantly higher in the leaf (5.33%) than the stem (0.262%). The Shannon-Weiner diversity index was H′ 0.8729, while Simpson index was higher in the leaf (0.583) than in the stem (0.416). Regarding the endophytic fungi’s potential for extracellular enzyme production, fluorogenic 4-methylumbelliferone standards and substrates were used to determine the presence of cellulases, phosphatases and glucosidases in the pure culture. Among fungal strains, Penicillum citrinum BSL17 showed significantly higher amounts of glucosidases (62.15±1.8 μM-1min-1mL) and cellulases (62.11±1.6 μM-1min-1mL), whereas Preussia sp. BSL10 showed significantly higher secretion of glucosidases (69.4±0.79 μM-1min-1mL) and phosphatases (3.46±0.31μM-1min-1mL) compared to other strains. Aureobasidium sp. BSS6 and Preussia sp. BSL10 showed significantly higher potential for indole acetic acid production (tryptophan-dependent and independent pathways). Preussia sp. BSL10 was applied to the host B. sacra tree saplings, which exhibited significant improvements in plant growth parameters and accumulation of photosynthetic pigments. The current study concluded that endophytic microbial resources producing extracellular enzymes and auxin could establish a unique niche for ecological adaptation during symbiosis with the host Frankincense tree.

Endophytes Aspergillus caespitosus LK12 and Phoma sp. LK13 of Moringa peregrina produce gibberellins and improve rice plant growth

Two new strains of endophytic fungi were isolated from the bark of Moringa peregrina and identified as Aspergillus caespitosus LK12 and Phoma sp. LK13. These endophytes were identified through amplifying polymerase chain reaction (PCR) and sequencing the 18S internal transcribed spacer of DNA extracted from both endophytes. Pure cultures of endophytic fungi were subjected to extract and isolate gibberellins (GAs). Deuterated standards of [17,17-2H2]-GA1, [17,17-2H2]-GA3, [17, 17-2H2]-GA4 and [17, 17-2H2]-GA7 were used to quantify the endophytic fungal GAs. The analysis revealed that both the endophytes are producing bioactive GAs in various quantities (ng mL−1). A. caespitosus LK12 was producing GA1 (54.51 ± 1.23), GA4 (26.5 ± 0.65), and GA7 (2.87 ± 1.23) while Phoma sp. LK13 was secreting GA1 (4.8 ± 0.12), GA3 (8.65 ± 0.21), GA4 (23.7 ± 0.98), and GA7 (22.7 ± 0.73). The culture filtrate (CF) of A. caespitosus and Phoma sp. significantly increased the shoot length of GAs-deficient mutant waito-c and normal Dongjin-beyo rice seedlings as compared to control. Application of such growth-promoting and GAs-producing endophytes can ameliorate poorly growing crop plants.

A fruitful decade from 2005 to 2014 for anthraquinone patents

Introduction: Anthraquinones are aromatic compounds whose structures are related to anthracene (parent structure: 9,10-dioxoanthracene) for which various methods for their synthesis have been developed. In the past decade (2005 – 2014), much work has been done regarding anthraquinone chemistry in order to discover new compounds related to this scaffold as anticancer, antibacterial, antidiabetic, antiviral, anti-HCV, antifibrotic, fungicidal and anti-inflammatory agents. Areas covered: This review covers the patents on therapeutic activities of anthraquinones and their derivatives in the years between 2005 and 2014. A large portion of the therapeutic applications that were reported in international patents will be presented and discussed. Although a large number of patents have been registered over the last decade, this review is focused on important patents related to cancer, inflammation, infectious diseases, diabetic conditions and hepatitis C. Expert opinion: The tricyclic planar ring system of anthraquinones displays a wide range of important pharmaceutical properties. By linking active anthraquinone analogs to other important pharmacophores or conjugates such as oximes, N-heterocycles, benzodiazepines or glycosyl ethers, their anticancer potential is enhanced. The ability of anthraquinone analogs to become more prominent as novel pharmaceutical agents may further be enhanced by fusing functionalized heterocyclic rings onto established anthraquinone cores.

Analgesic effects of crude extracts and fractions of Omani frankincense obtained from traditional medicinal plant Boswellia sacra on animal models.

OBJECTIVE To investigate the analgesic effect of Boswellia sacra (B. sacra), which could support the Omani traditional uses of frankincense for muscle, stomach, and arthritis pain. METHODS The crude extract, the essential oils and various sub-fractions of the crude methanol extract (each 300 mg/kg of the body weight of the animal) obtained from the resin of B. sacra were administered orally, and were evaluated for their analgesic activities by using two well known models of pain in mice, viz. acetic acid induced writhing test and formalin induced pain test in mice. RESULTS Of 13 samples, almost all of them were effective at an orally administered dose of 300 mg/kg of the body weight. The acetic acid induced writhes were inhibited in all the three phases with comparable values to the standard drug aspirin (300 mg/kg of body weight) with inhibition of 67.6% in phase I, 66.8% in phase II, and 37.9% in phase III. At the same time, all the tested samples were found effective in both the early and the late phases of formalin test. In formalin test, most of the tested samples showed more inhibitory effects as compared to the standard drug aspirin (300 mg/kg of body weight), which showed 36.2% and 29.6% inhibition in early and late phases respectively. Among the tested samples, the most significant inhibition was produced by Shabi frankincense oil (57.5% in early phase, and 55.6% in late phase). Interestingly, the extracts showed comparable percentage of inhibition to the oil and found in the following order: 60% chloroform/n-hexane sub-fraction (55.3% in early phase, and 66.7% in late phase), and 70% chloroform/n-hexane sub-fraction (59.6% in early phase, and 63.0% in late phase). CONCLUSIONS The present study provided the scientific justification about the analgesic properties of the essential oils, extract, and various sub-fractions obtained from the resin of B. sacra, thus validating its use in traditional folk medicines and other products; and hence supporting the development in the analgesic properties of bioactive natural substances.

Antimicrobial chemical constituents from endophytic fungus Phoma sp.

Abstract Objective To evaluate the antimicrobial potential of different extracts of the endophytic fungus Phoma sp. and the tentative identification of their active constituents. Methods The extract and compounds were screened for antimicrobial activity using the Agar Well Diffusion Method. Four compounds were purified using column chromatography and their structures were assigned using 1 H and 13 C NMR spectra, DEPT, 2D COSY, HMQC and HMBC experiments. Results The ethyl acetate fraction of Phoma sp. showed good antifungal, antibacterial, and algicidal properties. One new dihydrofuran derivative, named phomafuranol (1), together with three known compounds, phomalacton (2), (3R)-5-hydroxymellein (3) and emodin (4) were isolated from the ethyl acetate fraction of Phoma sp. Preliminary studies indicated that phomalacton (2) displayed strong antibacterial, good antifungal and antialgal activities. Similarly (3R)-5-hydroxymellein (3) and emodin (4) showed good antifungal, antibacterial and algicidal properties. Conclusions Antimicrobial activities of the ethyl acetate fraction of the endophytic fungus Phoma sp. and isolated compounds clearly demonstrate that Phoma sp. and its active compounds represent a great potential for the food, cosmetic and pharmaceutical industries.

Regulations of essential amino acids and proteomics of bacterial endophytes Sphingomonas sp. Lk11 during cadmium uptake

Endophytic bacteria have been recently known for their potential to bioaccumulate metal from contaminated mediums. However, little is known about the physiological responses of phytohormone producing (gibberellins and auxins) endophytes during metal stressed environment. Endophytic bacteria Sphingomonas sp. LK11 was assessed for metals bioaccumulation and its physiological responses towards metal stress. The endophyte was grown in cadmium (Cd), zinc (Zn), aluminum (Al), manganese (Mn), and copper (Cu) contaminated mediums. The results revealed significantly higher endophytic growth potentials in Cd, Cu and Zn contaminations; however, the bio‐accumulation rate of Cd was more prolific as compared to Zn and Cu. Interestingly, the SDS‐PAGE profile showed increased expressions of proteins in Zn and Cu than in Cd. A similar attenuate response of amino acids was also observed for Cd than in case of Zn and Cu. Only asparagine, glutamate and proline showed significant impact in Cd while Cu and Zn had significantly higher responses of almost all amino acids. Detailed protein profile showed the activation of chaperone, antioxidative and detoxification proteins. Increased regulations of oxidoreductases, superoxide dismutase, thioredoxin, malate dehydrogenase, 2‐oxoisovalerate dehydrogenase, 2‐oxoisovalerate dehydrogenase, and dihydrolipoyl dehydrogenase were observed. The cellular defense‐related protein responses were potent against Cd stress. The results conclude that Sphingomonas sp. LK11 reprogram its amino acids and proteomic expressions and maintain a steady growth during Cd stress. Using such phytohromones producing endophytic bacterium can be ideal approach to increase the phytoextraction potential of metal remediating plants.

Sorokiniol: a new enzymes inhibitory metabolite from fungal endophyte Bipolaris sorokiniana LK12.

BackgroundMedicinal plants harboring endophytic fungi could carry significant potential for producing bioactive secondary metabolites. Endophytic fungi serve as alternate source of interesting compounds in their natural and modified synthetic forms to treat different diseases. In this regard, endophytic microflora associated with alkaloid-rich medicinal plants Rhazya stricta is least known.ResultsWe isolated one new bioactive compound sorokiniol (1) along with two known cyclic peptides BZR-cotoxin I (2) and BZR-cotoxin IV (3) from fungal endophyte Bipolaris sorokiniana LK12. The structures of the isolated new and known compounds were elucidated through spectroscopic data, including 1D and 2D NMR (1H, 13C, HSQC, HMBC, and NOESY), mass, and UV. The known peptides (2–3) were characterized by ESI-MS, MS/MS, and by comparing the NMR data with the literature. The isolated metabolites were assayed for their role against enzyme inhibition. Compound 1 was significantly inhibitory towards acetyl cholinestrase while the other compounds (2–3) had moderate anti-lipid peroxidation and urease activities.ConclusionThe present results suggest that the endophytic microorganism associated with indigenously important medicinal plants can offer a rich source of biologically active chemical constituents which could help in discovering enzyme inhibitory lead drugs.