Modern Approaches in the Discovery and Development of Plant-Based Natural Products and Their Analogues as Potential Therapeutic Agents.

Natural products represents an important source of new lead compounds in drug discovery research. Several drugs currently used as therapeutic agents have been developed from natural sources; plant sources are specifically important. In the past few decades, pharmaceutical companies demonstrated insignificant attention towards natural product drug discovery, mainly due to its intrinsic complexity. Recently, technological advancements greatly helped to address the challenges and resulted in the revived scientific interest in drug discovery from natural sources. This review provides a comprehensive overview of various approaches used in the selection, authentication, extraction/isolation, biological screening, and analogue development through the application of modern drug-development principles of plant-based natural products. Main focus is given to the bioactivity-guided fractionation approach along with associated challenges and major advancements. A brief outline of historical development in natural product drug discovery and a snapshot of the prominent natural drugs developed in the last few decades are also presented. The researcher's opinions indicated that an integrated interdisciplinary approach utilizing technological advances is necessary for the successful development of natural products. These involve the application of efficient selection method, well-designed extraction/isolation procedure, advanced structure elucidation techniques, and bioassays with a high-throughput capacity to establish druggability and patentability of phyto-compounds. A number of modern approaches including molecular modeling, virtual screening, natural product library, and database mining are being used for improving natural product drug discovery research. Renewed scientific interest and recent research trends in natural product drug discovery clearly indicated that natural products will play important role in the future development of new therapeutic drugs and it is also anticipated that efficient application of new approaches will further improve the drug discovery campaign.

Study of influence of Catha edulis (Khat) chewing on oral pharmacokinetics of irbesartan in rats using a newly developed HPLC-UV method.

Khat consumers might use a number of drugs for underlying conditions; however the potential drug-herb interaction between khat and other drugs including Irbesartan (IRB) is unknown. The present study was conducted to evaluate the effects of khat chewing on pharmacokinetic profile of IRB, a commonly available antihypertensive agent. The pharmacokinetic profile of orally administered IRB (15.5 mg/kg) with and without pre-administration of khat (12.4 mg/kg) were determined in Sprague-Dawley rats. IRB was estimated in rat plasma samples using a newly developed HPLC method. The chromatographic separation of the drug and internal standard (IS) was performed on a C-18 column (Raptor C-18, 100 mm × 4.6 mm id.; 5 µm) using a mobile phase consisting of 10 mM ammonium acetate buffer (pH 4.0) and acetonitrile in a ratio 60:40 v/v. Acceptable linearity for IRB was recorded at 1 - 12 µg/mL concentration range (R2 > 0.99). Intra-day and inter-day precision (%RSD = 0.44% - 3.27% and 0.39-1.98% respectively) and accuracy (% recovery = 98.3 - 104.3%) in rat plasma was within the acceptable limit according to USFDA guidelines. The AUC0-t was found to be significantly increased in IRB-khat co-administered rats as compared to rats receiving IRB only; whereas, the Tmax (0.5 h) value remained unchanged. Results of this study revealed that the IRB level considerably increased in rat plasma upon co-administration of khat. This might be due to the inhibition of CYP2D9 by khat which is the principal cytochrome P450 isoform responsible for IRB metabolism.

Analysis of amphetamine and methamphetamine contents in seized tablets from Jazan, Saudi Arabia by liquid chromatography-mass spectroscopy (LC-MS/MS) and chemometric techniques.

A number of illegal amphetamine tablets were seized from three different cities of Jazan province of southern Saudi Arabia and were analyzed for amphetamine and methamphetamine contents using LC-MS/MS technique. Analyses were performed using a previously reported method taking 0.1 M ammonium formate buffer (85%) and 15% acetonitrile with 0.1% formic acid as mobile phase with a total runtime of 12 min. This method was successfully applied for the routine analysis of amphetamine and methamphetamine in the seized tablets using amphetamine-D5 and methamphetamine-D5 as internal standards. Hierarchical cluster analysis was performed to establish the similarity between samples. The retention times (RT) for internal standard, amphetamine and methamphetamine were observed to be within 6.0-7.1 min. Ten tablet samples from each city were subjected to analysis and the amount of amphetamine in all the samples were found to be in the range of 9.07-14.77 mg, whereas, the amount of methamphetamine ranged from 0.12 to 0.24 mg in each tablet. Hierarchical cluster analysis showed presence of five clusters of samples indicating different characteristics and possible sources of amphetamine tablets. The largest cluster consisted of 15 samples which are expected to be of the same origin. Both amphetamine and methamphetamine are considered to be illegal products and their illegal trade and use is banned in many countries including Saudi Arabia. Therefore, there is an urgent need of strict regulations worldwide to check the illicit trafficking of these psychoactive substances and should be considered on priority.

Risk-based exposure assessment for multiple toxic elements encountered by children in school playgrounds and parks in the southwest region of Saudi Arabia.

Children are in direct contact with surface soil and may inadvertently ingest and inhale toxic contaminants while playing; hence, special attention should be given to playgrounds regarding toxic contaminants. The concentrations of ten toxic metals were determined in soil samples collected from school playgrounds and children's parks from the southwest region of Saudi Arabia. The soils were moderately alkaline (pH 7.6-8.8), the texture was dominated by sand particles (54-88%), and the organic matter was in the range of 2.06 to 4.82%. Analytical solutions were prepared by microwave-digestion using a HNO3/H2O2 mixture, and the concentrations of toxic elements were measured by inductively coupled plasma mass spectrometry (ICP-MS). Metal concentrations were recorded in the range of 0.014-0.087, 1.14-3.54, 0.85-23.29, 0.77-36.32, 312.6-2065.7, 285.3-822.6, 75.4-240.8, 0.00-53.12, 0.52-6.80, and 1.25-92.12 mg/kg dry soil for Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, and Zn, respectively. The levels of heavy metals in the studied playgrounds were below the permissible limits, indicating insignificant influence of anthropogenic activities and can be considered as unpolluted soil. Values of the enrichment coefficient (EC) and contamination factor (CF) were found to be less than one, suggesting that the source of these elements is mainly the local soil, with the exception of Ni and Zn in certain playgrounds (CF > 1), which indicates a possible contamination from external sources. The non-carcinogenic hazard index calculated for all of the metals was below one, indicating that the exposure to heavy metal through playground soil is unlikely to produce any adverse health effect in children playing in the playgrounds.

Targeting PD-1/PD-L-1 immune checkpoint inhibition for cancer immunotherapy: success and challenges.

The programmed death-1 receptor (PD-1) acts as a T-cell brake, and its interaction with ligand-1 (PD-L-1) interferes with signal transduction of the T-cell receptor. This leads to suppression of T-cell survival, proliferation, and activity in the tumor microenvironment resulting in compromised anticancer immunity. PD-1/PD-L-1 interaction blockade shown remarkable clinical success in various cancer immunotherapies. To date, most PD-1/PD-L-1 blockers approved for clinical use are monoclonal antibodies (mAbs); however, their therapeutic use are limited owing to poor clinical responses in a proportion of patients. mAbs also displayed low tumor penetration, steep production costs, and incidences of immune-related side effects. This strongly indicates the importance of developing novel inhibitors as cancer immunotherapeutic agents. Recently, advancements in the small molecule-based inhibitors (SMIs) that directly block the PD-1/PD-L-1 axis gained attention from the scientific community involved in cancer research. SMIs demonstrated certain advantages over mAbs, including longer half-lives, low cost, greater cell penetration, and possibility of oral administration. Currently, several SMIs are in development pipeline as potential therapeutics for cancer immunotherapy. To develop new SMIs, a wide range of structural scaffolds have been explored with excellent outcomes; biphenyl-based scaffolds are most studied. In this review, we analyzed the development of mAbs and SMIs targeting PD-1/PD-L-1 axis for cancer treatment. Altogether, the present review delves into the problems related to mAbs use and a detailed discussion on the development and current status of SMIs. This article may provide a comprehensive guide to medicinal chemists regarding the potential structural scaffolds required for PD-1/PD-L-1 interaction inhibition.

Heavy Metal Contamination in Leafy Vegetables Grown in Jazan Region of Saudi Arabia: Assessment of Possible Human Health Hazards.

The food chain, through vegetable consumption, is considered to be an important route of heavy metal exposure. Therefore, in this study, heavy metal concentrations in leafy vegetables grown in the Jazan region of Saudi Arabia were assessed using an ICP-MS. Lettuce, radish, mint, parsley and jarjir (Arugula) were selected for study and subjected to digestion using HCl. The results indicated that the Fe level was highest in all vegetables, while jarjir was the most contaminated vegetable. However, no tested metal exceeded the maximum permissible limits set by the FAO/WHO and European Committee. The possible health hazards associated with the exposure to metal contaminants via vegetable consumption were evaluated by estimating target hazard quotient (THQ) values, and the results revealed that the vegetables grown in close proximity of Jazan city were the most contaminated and those in Darb the least. However, the daily intakes of all the tested metals were well below the corresponding oral reference doses (RfDs), and the THQ values were less than unity, suggesting that the vegetables grown in the studied region were safe and the heavy metal exposure via vegetable consumption was unlikely to cause adverse effects to the local inhabitants of the region.

Phytochemical, Cytotoxic, and Antimicrobial Evaluation of Tribulus terrestris L., Typha domingensis Pers., and Ricinus communis L.: Scientific Evidences for Folkloric Uses.

Many medicinal plants have been utilized for centuries despite the lack of scientific evidence of their therapeutic effects. This study evaluated the phytochemical and dual biological profiling, namely, antibacterial and cytotoxic properties, of three plant species, namely, Tribulus terrestris L., Typha domingensis Pers., and Ricinus communis L., in order to explore potential relationships (if any) with their ethnopharmacological uses. GC-MS was used to achieve phytochemical screening of two plant extracts (T. terrestris and T. domingensis). The primary chemicals detected in varying amounts in both extracts were siloxane derivatives, fatty acid esters, diisooctyl phthalate, phytosterol, and aromatic acid esters. According to the findings, the major component detected in both extracts was 1,2-benzenedicarboxylic acid and diisooctyl ester (antibacterial and antifungal). T. domingensis contained a low level of benzoic acid, methyl ester (antibacterial). Both extracts included stigmasterol and sitosterol, as well as six different forms of fatty acid esters. Antimicrobial, antioxidant, anticancer, thyroid inhibitor, and anti-inflammatory properties have all been described. Human breast adenocarcinoma (MCF7), human ovary adenocarcinoma (A2780), and human colon adenocarcinoma (HT29), as well as normal human fetal lung fibroblasts (MRC5), all showed cytotoxic activity. The most potent activity against A2780 cells was seen in T. terrestris and T. domingensis extracts (IC50: 3.69 and 5.87 g/mL, respectively). R. communis was more active against MCF7 cells (1.52 µg/mL) followed by A2780 and HT29 cells, respectively. R. communis showed a dose-dependent clonogenic effect against MCF7 cells. The antibacterial activity of all three plant extracts was tested against three standard Gram-positive, four standard Gram-negative, and two clinical bacterial strains. Among the three extracts examined, T. terrestris was the most effective, followed by R. communis, and finally, T. domingensis plant extract was effective against various isolated bacteria. This study, interestingly, sheds light on the bioactive components found in plant extracts that can be utilized for cytotoxic and antibacterial purposes.

Spectroscopic characterization of the interactions of bovine serum albumin with medicinally important metal ions: platinum (IV), iridium (III) and iron (II).

Serum albumin protein plays a key role in the transportation and distribution of bioactive species including metal ions and metal-based drugs and, therefore, the nature of their binding could provide important insight for the development of new drugs. In the present investigation, binding interactions of bovine serum albumin (BSA) with three biologically important metal ions: Pt4+, Ir3+ and Fe2+ were screened using easy-to-use and cost-effective Fourier-Transform Infrared (FT-IR) and Ultraviolet-Visible (UV-Vis) spectroscopic techniques. Prior to the screening, the protein and metal ions were allowed to interact at physiological pH (7.4) and the spectral changes were monitored upon interaction. In FT-IR spectrum, the position of amide I band (C=O stretching) was shifted from 1652 cm-1 in case of free BSA to 1659, 1657 and 1656 cm-1 in BSA-Pt4+, BSA-Ir3+ and BSA-Fe2+ complexes, respectively. This spectral shifting was due to the binding of metal ions to N and O atoms of BSA peptide bonds. The interaction was further demonstrated by a remarkable reduction in spectral intensities of amide I and II bands. Secondary protein structure analysis revealed conformational changes characterized by a substantial decrease in α-helix (11.29-27.41%) accompanied by an increase in ß-sheet and ß-antiparallel contents. The absorption of BSA at a constant concentration at 280 nm was successively reduced as the concentration of Pt4+ and Ir3+ ions increased. On the other hand, the absorption of BSA-Fe2+ complex successively increased with the increase in the concentration of Fe2+ in the test solution. The binding constants for BSA-Pt4+, BSA-Ir3+ and BSA-Fe2+ complexes were calculated to be 1.55×104, 5.67×104 and 3.78×104 M-1, respectively. The results revealed that the three metal ions showed binding affinities with the BSA protein in the order: Ir3+>Fe2+>Pt4+.

Medicinal Plants and Isolated Molecules Demonstrating Immunomodulation Activity as Potential Alternative Therapies for Viral Diseases Including COVID-19.

Plants have been extensively studied since ancient times and numerous important chemical constituents with tremendous therapeutic potential are identified. Attacks of microorganisms including viruses and bacteria can be counteracted with an efficient immune system and therefore, stimulation of body's defense mechanism against infections has been proven to be an effective approach. Polysaccharides, terpenoids, flavonoids, alkaloids, glycosides, and lactones are the important phytochemicals, reported to be primarily responsible for immunomodulation activity of the plants. These phytochemicals may act as lead molecules for the development of safe and effective immunomodulators as potential remedies for the prevention and cure of viral diseases. Natural products are known to primarily modulate the immune system in nonspecific ways. A number of plant-based principles have been identified and isolated with potential immunomodulation activity which justify their use in traditional folklore medicine and can form the basis of further specified research. The aim of the current review is to describe and highlight the immunomodulation potential of certain plants along with their bioactive chemical constituents. Relevant literatures of recent years were searched from commonly employed scientific databases on the basis of their ethnopharmacological use. Most of the plants displaying considerable immunomodulation activity are summarized along with their possible mechanisms. These discussions shall hopefully elicit the attention of researchers and encourage further studies on these plant-based immunomodulation products as potential therapy for the management of infectious diseases, including viral ones such as COVID-19.

A Fast and Validated Reversed-Phase HPLC Method for Simultaneous Determination of Simvastatin, Atorvastatin, Telmisartan and Irbesartan in Bulk Drugs and Tablet Formulations.

The aim of this study was to develop and validate a fast and simple reversed-phase HPLC method for simultaneous determination of four cardiovascular agents-atorvastatin, simvastatin, telmisartan and irbesartan in bulk drugs and tablet oral dosage forms. The chromatographic separation was accomplished by using Symmetry C18 column (75 mm × 4.6 mm; 3.5 µ) with a mobile phase consisting of ammonium acetate buffer (10 mM; pH 4.0) and acetonitrile in a ratio 40:60 v/v. Flow rate was maintained at 1 mL/min up to 3.5 min, and then suddenly changed to 2 mL/min till the end of the run (7.5 min). The data was acquired using ultraviolet detector monitored at 220 nm. The method was validated for linearity, precision, accuracy and specificity. The developed method has shown excellent linearity (R² > 0.999) over the concentration range of 1-16 µg/mL. The limits of detection (LODs) and limits of quantification (LOQs) were in the range of 0.189-0.190 and 0.603-0.630 µg/mL, respectively. Inter-day and intra-day accuracy and precision data were recorded in the acceptable limits. The new method has successfully been applied for quantification of all four drugs in their tablet dosage forms with percent recovery within 100 ± 2%.

1,3,4-Oxadiazole/thiadiazole and 1,2,4-triazole derivatives of biphenyl-4-yloxy acetic acid: synthesis and preliminary evaluation of biological properties.

A series of 1,3,4-oxadiazole/thiadiazole and 1,2,4-triazole derivatives of biphenyl-4-yloxy acetic acid were synthesized in order to obtain new compounds with potential anti-inflammatory activity, analgesic activity and lower ulcerogenic potential. All compounds were evaluated for their anti-inflammatory activity by the carrageenan induced rat paw edema test method. The compounds possessing potent anti-inflammatory activity were further tested for their analgesic, ulcerogenic and antioxidant activities. Out of all tested compounds, the compounds 3, 7, 17 and 20, showed significant reduction in rat paw edema induced by carrageenan treatment. These compounds showed significant analgesic effect and at an equimolar oral doses relative to flurbiprofen were also found to be non-gastrotoxic in rats. Compound 17 was evaluated as the lead compound having more anti-inflammatory activity (81.81%) than the reference drug (79.54%), low ulcerogenic potential and protective effect on lipid peroxidation.

Synthesis and pharmacological evaluation of condensed heterocyclic 6-substituted-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole derivatives of naproxen.

Some 6-substituted-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole derivatives (4a-f and 5a-d) have been synthesized by cyclisation of 4-amino-5-[1-(6-methoxy-2-naphthyl)ethyl]-3-mercapto-(4H)-1,2,4-triazole (3) with various substituted aromatic acids and aryl/alkyl isothiocyanates, through a single step reaction. The target compounds were pharmacologically evaluated for their anti-inflammatory and analgesic potentials by known experimental models. Several of these showed significant activity. Very low ulcerogenic index was observed for potent compounds.

Non-carboxylic analogues of naproxen: design, synthesis, and pharmacological evaluation of some 1,3,4-oxadiazole/thiadiazole and 1,2,4-triazole derivatives.

A series of substituted 1,3,4-oxadiazole (2-7 and 14-19), 1,2,4-triazole (20-25), and 1,3,4-thiadiazole (26-31) derivatives of naproxen have been synthesized by cyclization of 2-(6-methoxy-2-naphthyl)propanoic acid hydrazide 1 and N(1)[2-(6-methoxy-2-naphthyl) propanoyl]-N(4)-alkyl/aryl-thiosemicarbazides (8-13) under various reaction conditions. All the compounds were screened for their anti-inflammatory activity by carrageenan-induced rat paw edema test method. Compounds showing high anti-inflammatory activity were also tested for their analgesic, ulcerogenic, and lipid peroxidation. Few of the synthesized compounds showed significant anti-inflammatory and analgesic activities along with reduced ulcerogenic effect and lipid peroxidation.