Ahmed Al-Harrasi

Chemistry and biology of genus Vismia

Context: Many herbal remedies have been employed in the treatment and management of various human ailments since the beginning of human civilization. Vismia is an extensive genus of the family Hypericaceae and consists of small trees inhabiting the tropical and subtropical regions of South and Central America. Within the framework of an International Cooperative Biodiversity Groups project, three Vismia species were studied for their potential anticancer activity. Objectives: This review is an extensive study of the available scientific literature published and comprises of the ethnopharmacological, phytochemical and therapeutic potential of genus of plants under the umbrella Vismia. Methods: The present review includes 134 natural products with 47 references compiled from the major databases, viz., Chemical Abstracts, Science Direct, SciFinder, PubMed, Dr. Dukes Phytochemical and Ethnobotany, CIMER, and InteliHealth. Results: An exhaustive survey of the accessed literature revealed that flavonoids, flavanols, xanthones, anthraones, anthraquinones, benzophenones, lignans, steroids, monoterpenes and triterpenes constituted the major classes of phytoconstituents of this genus. Pharmacological reports revealed that it is used for skin diseases such as dermatitis, leprosy, syphilis, herpes, scabies and eczemas, and as an anticancer for human breast, CNS, and lung cancer cell lines. Conclusion: Genus Vismia plants seem to hold great potential for an in-depth investigation towards discovering biological activities, especially for the treatment of cancers affecting our society. Through this review, the authors hope to attract the attention of natural product researchers throughout the world to focus on the unexplored potential of Vismia plants, with the view of developing new formulations with an improved therapeutic value.

Antiglycation therapy: Discovery of promising antiglycation agents for the management of diabetic complications

Abstract Context: During diabetes mellitus, non-enzymatic reaction between amino groups of protein and carbonyl of reducing sugars (Millard reaction) is responsible for the major diabetic complications. Various efforts have been made to influence the process of protein glycation. Objectives: This review article provides an extensive survey of various studies published in scientific literature to understand the process of protein glycation and its measurement. Moreover, evaluation and identification of potential inhibitors (antiglycation agents) of protein glycation from natural and synthetic sources and their mechanism of action in vitro and in vivo are also addressed. Method: In this review article, the mechanism involved in the formation of advanced glycation end products (AGEs) is discussed, while in second and third parts, promising antiglycation agents of natural and synthetic sources have been reviewed, respectively. Finally, in vivo studies have been addressed. This review is mainly compiled from important databases such as Science, Direct, Chemical Abstracts, SciFinder, and PubMed. Results: During the last two decades, various attempts have been made to inhibit the process of protein glycation. New potent inhibitors of protein glycation belonging to different classes such as flavonoids, alkaloids, terpenes, benzenediol Schiff bases, substituted indol, and thio compounds have been identified. Conclusion: Antiglycation therapy will be an effective strategy in future to prevent the formation of AGEs for the management of late diabetic complications Current review article highlighted various compounds of natural and synthetic origins identified previously to inhibit the protein glycation and formation of AGEs in vitro and in vivo.

α-Glucosidase Enzyme Inhibitors From Natural Products

Diabetes mellitus characterized by hyperglycemia is one of the most important health issues worldwide. Diabetes mellitus is spreading very rapidly while currently available drugs to manage diabetes are associated with many serious side effects. Among a number of diabetic targets, α-glucosidase is regarded as an important therapeutic target to manage hyperglycemic conditions. The inhibitors of α-glucosidase enzyme actually slow down the digestion and absorption of carbohydrates and thus decrease the insulin demand. In this way, the sudden increase in blood glucose level after a meal can be controlled independently of insulin. Currently, efficacious α-glucosidase inhibitors with low toxicity are highly desirable. Several medicinal plants have been evaluated for their potential role against α-glucosidase enzyme. In this chapter, we wish to offer an overview on α-glucosidase inhibitors occurring from natural sources reported during the period 2000–15.

Molecular players of auxin transport systems: advances in genomic and molecular events

ABSTRACT Phytohormone auxin plays an indispensable role in the plethora of plant developmental process starting from the cell division, and cell elongation to morphogenesis. Auxins are transported to different parts of the plant by different sophisticated transporter molecules known as ‘auxin transporters’.There are four auxin transporter families that have been reported so far in the plant kingdom which includes AUX/LAX (AUXIN-RESISTANT1–LIKES), PIN (PIN-FORMED, auxin efflux carriers), ABCB ((ATP-binding cassette-B (ABCB)/P-glycoprotein (PGP)) and PILS (PIN-Likes). Auxin influx and efflux carriers are distributed in a polar fashion in the plasma membrane whereas ABCB and PILS are present in a non-polar fashion. Other than AUX/LAX, other auxin transporters harbor N-and C-terminal conserved domains along with a variable hydrophilic loop in the transmembrane domain. The AUX/LAX, ABCB and PIN transporters mediate long distance auxin transport whereas PILS and PIN5 protein involved in intracellular auxin homeostasis.

Early Events in Plant Abiotic Stress Signaling: Interplay Between Calcium, Reactive Oxygen Species and Phytohormones

Upon exposure to abiotic stresses, plants activate early stress-signaling mechanisms within a few seconds to a few hours to counter the stress responses and bring tolerance. The most versatile signaling molecules involved during the early events of abiotic stress signaling are Ca2+ (calcium ion) and reactive oxygen species (ROS), 1O2, O2−, and H2O2. Initially, apoplastic Ca2+ activates plasma membrane-bound NADPH oxidase and generates H2O2, which acts as a second messenger and further leads to the activation of downstream signaling processes. Subsequently, H2O2 activates calcium-dependent protein kinase (CDPK) and mitogen activated protein kinase (MAPK) pathways, leading to stress tolerance through downstream signaling cascades. In addition, fast influx of Ca2+ from the apoplast to the cytosol further activates cytosolic CDPKs and respiratory burst oxidase D and regulates Ca2+ and ROS signaling. Sub-cellular organelles further produce ROS and Ca2+ to bring stress tolerance. Excessive ROS produced during these processes are quenched by ROS scavenging enzymes, whereas excessive Ca2+ is neutralized by the action of the calcium binding proteins CDPKs, CaMs, CMLs, and CBLs. The phytohormone ABA further regulates the production of H2O2, thus maintaining the positive feedback system for ROS production and stress tolerance. Additionally, CBL proteins modulate H2O2 production in the presence of NADPH oxidase via interaction with CIPK, thus maintaining a positive feedback mechanism in stress tolerance. Similarly, CaM proteins bind with MAPK and regulate stress tolerance by activating the MAPK cascade.

Complete genome sequencing and analysis of endophytic Sphingomonas sp. LK11 and its potential in plant growth

Our study aimed to elucidate the plant growth-promoting characteristics and the structure and composition of Sphingomonas sp. LK11 genome using the single molecule real-time (SMRT) sequencing technology of Pacific Biosciences. The results revealed that LK11 produces different types of gibberellins (GAs) in pure culture and significantly improves soybean plant growth by influencing endogenous GAs compared with non-inoculated control plants. Detailed genomic analyses revealed that the Sphingomonas sp. LK11 genome consists of a circular chromosome (3.78 Mbp; 66.2% G+C content) and two circular plasmids (122,975 bps and 34,160 bps; 63 and 65% G+C content, respectively). Annotation showed that the LK11 genome consists of 3656 protein-coding genes, 59 tRNAs, and 4 complete rRNA operons. Functional analyses predicted that LK11 encodes genes for phosphate solubilization and nitrate/nitrite ammonification, which are beneficial for promoting plant growth. Genes for production of catalases, superoxide dismutase, and peroxidases that confer resistance to oxidative stress in plants were also identified in LK11. Moreover, genes for trehalose and glycine betaine biosynthesis were also found in LK11 genome. Similarly, Sphingomonas spp. analysis revealed an open pan-genome and a total of 8507 genes were identified in the Sphingomonas spp. pan-genome and about 1356 orthologous genes were found to comprise the core genome. However, the number of genomes analyzed was not enough to describe complete gene sets. Our findings indicated that the genetic makeup of Sphingomonas sp. LK11 can be utilized as an eco-friendly bioresource for cleaning contaminated sites and promoting growth of plants confronted with environmental perturbations.

Evaluation of essential oils from Boswellia sacra and Teucrium mascatense against acetyl cholinesterase enzyme and urease enzyme

Enzyme inhibition is one of the most important areas of pharmaceutical research which resulted in the discoveries of several useful drugs. The prime aim of this study is to identify effective natural inhibitors against pharmacologically important enzymes such as acetylcholinesterase enzyme and urease enzyme. In present study, we evaluated the essential oils extracted from medicinally important plants including Boswellia sacra Fluckiger (frankincense) and Teucrium mascatense Boiss. Two major constituents of frankincense essential oil including (+)-α-pinene and (R)-+-limonene were also investigated against these enzymes. The essential oils were extracted from Boswellia sacra and Teucrium mascatense which are native plants to the southern and northern areas of Oman, respectively. In this study, the essential oil of frankincense exhibited significant inhibition with IC 50 value of 0.043±0.02 mg/mL, against acetylcholinesterase enzyme while against urease enzyme it has shown good inhibition with IC 50 value of 0.17 ± 0.05 mg/mL. The essential oil obtained from the Teucrium mascatense was found to be in active against both the enzymes. On acetylcholinesterase enzyme inhibition assay, the (+)-α- pinene exhibited significant inhibition (IC 50 = 0.094±0.01 mg/mL) while (R)-+- limonene was found to be inactive on this assay. Against urease enzyme (+)-α- pinene and (R)-+- limonene showed moderate activity 40.06±1.03 % and 19.5±1.00 %, respectively. Interestingly, the mixture of equal concentration of (+)-α- pinene and (R)-+- limonene exhibited 70% inhibition with IC 50 value of (0.195 ± 0.10 mg/mL) which shows the synergistic relationship between them. Promising inhibitory potential of frankincense essential oil and (+)-α-pinene, against acetylcholinesterase enzyme and urease enzyme indicated their potential therapeutic role to manage Alzheimer’s disease and stomach ulcers, respectively.