Enzymes Inhibition and Antioxidant Potential of Medicinal Plants Growing in Oman

Effects of age and tissue of Juniperus sabina L. on its phytochemical characteristics, anti-cholinesterase, antidiabetes, and anti-drug resistant bacteria activities

Juniperus sabina L. is used in the traditional Chinese medicine (TCM) system to prevent or treat various diseases. However, only the leaves and branches are used as medicinal parts. The aim of this study was to compare the chemical characteristics of different tissues (leaves, branches, stems, and roots) of J. sabina at different ages by HPLC-MS and to evaluate the biological activity (enzyme inhibition, anti-drug-resistant bacteria). Total phenol (TPC) and total lignan (TLC) contents in J. sabina were determined by Folin-Ciocalteu method and UV spectrophotometry, respectively. High levels of total phenols (87.16 mg GAE/g dry weight) and total lignans (491.24 mg PPT/g dry weight) were detected in fifteen annual J. sabina roots and current year leaves, respectively. Eleven compounds, of which six were phenolic compounds and five were lignans, were identified and quantified by HPLC/HPLC-MS. Statistical analysis showed that the distribution and content of the detected compounds showed considerable variation among ages and tissues, and that the current year leaves of fifteen annual J. sabina could be used as a potential application site for the source of podophyllotoxin. Acetylcholinesterase (AChE) inhibitory activity was found to be the highest on the extracts of fifteen annual J. sabina current year leaves (47.37 μg/mL), while the highest inhibition towards butyrylcholinesterase (BChE) was observed for the extracts of seven annual J. sabina previous year leaves (136.3 μg/mL). And the second annual J. sabina current year stem's extracts showed the best antidiabetic activity (anti-α-glucosidase, 62.59 μg/mL). In addition, the extracts of fifteen annual J. sabina roots (47.37 μg/mL) showed the highest anti-MRSA activity (31.25 μg/mL). Redundancy analysis (RDA) was conducted to clarify the factors affecting the biological activity of J. sabina, and its results showed that epicatechin and matairesinol showed positive promotion. This study provides a new perspective for understanding the chemical differences and comprehensive utilization of different tissues of J. sabina.

Phytochemical Screening and In Vitro Evaluation of the Antioxidant Potential of Dichloromethane Extracts of Strychnos henningsii Gilg. and Ficus sycomorus L

Medicinal plants are a rich source of antioxidants such as flavonoids, phenols, tannins, and alkaloids among others and are currently used as alternative and complementary drugs in the management of stress-related disorders. Strychnos henningsii and Ficus sycomorus have been traditionally used by the people of Mbeere, Embu county, Kenya, as medicine for the treatment of various oxidative stress-related disorders such as diabetes and rheumatism; however, no empirical data are available to authenticate the said claim. The aim of this study was to evaluate preliminary phytochemical screening and in vitro antioxidant activity of dichloromethane (DCM) leaf extract of S. henningsii and stem bark extract of F. sycomorus using DPPH, hydrogen peroxide, and ferric reducing power assays; total flavonoids and phenolic compounds were also determined by colorimetric assay and Folin–Ciocalteu reaction, respectively. Phytochemical screening showed that both extracts possessed saponins, flavonoids, phenols, steroids, alkaloids, and cardiac glycosides; however, terpenoids were found to be absent in S. henningsii. The total phenolic and flavonoid content of the DCM stem bark extract of F. sycomorus was lower than that of the leaf extract of S. henningsii. These extracts significantly exhibited strong antioxidant activities at different concentrations tested. The IC50 values of S. henningsii and F. sycomorus were 0.325 mg/ml and 0.330 mg/ml for hydrogen peroxide and 0.068 mg/ml and 0.062 mg/ml for DPPH, respectively. Both DCM leaf and stem bark extracts of S. henningsii and F. sycomorus were found to have strong ferric reducing power. Therefore, both extracts showed significant nonenzyme-based antioxidant activities. The two plants possess phytochemicals that have significant antioxidant properties.

Bio-Oriented Synthesis of Novel Polyhydroquinoline Derivatives as α-Glucosidase Inhibitor for Management of Diabetes

Polyhydroquinoline derivatives (1-15) were synthesized through an unsymmetrical Hantzsch reaction in excellent yields by treating 3,5-dibromo-4-hydroxybenzaldehyde, dimedone, ammonium acetate, and ethyl acetoacetate in ethanol solvent. The structures of the synthesized compounds (1-15) were deduced through different spectroscopic techniques such as 1H NMR, 13C NMR, and HR-ESI-MS. The synthesized products were tested for their α-glucosidase inhibitory activity where compounds 11 (IC50 = 0.56 ± 0.01 μM), 10 (IC50 = 0.94 ± 0.01 μM), 4 (IC50 = 1.47 ± 0.01 μM), 2 (IC50 = 2.20 ± 0.03 μM), 6 (IC50 = 2.20 ± 0.03 μM), 12 (IC50 = 2.22 ± 0.07 μM), 7 (IC50 = 2.76 ± 0.04 μM), 9 (IC50 = 2.78 ± 0.03 μM), and 3 (IC50 = 2.88 ± 0.05 μM) exhibited high potential for the inhibition of α-glucosidase, while the rest of the compounds (8, 5, 14, 15, and 13) showed significant α-glucosidase inhibitory potential with IC50 values of 3.13 ± 0.10, 3.34 ± 0.06, 4.27 ± 0.13, 6.34 ± 0.15, and 21.37 ± 0.61 μM, respectively. Among the synthesized series, two compounds, i.e., 11 and 10, showed potent α-glucosidase inhibitory potential higher than the standard. All the compounds were compared with standard drug "acarbose" (IC50 = 873.34 ± 1.67 μM). An in silico method was used to predict their mode of binding within the active site of enzyme to understand their mechanism of inhibition. Our in silico observation complements with the experimental results.

Synthesis of new phenoxymethylcoumarin clubbed 4-arylthiazolylhydrazines as α-glucosidase inhibitors and their kinetics and molecular docking studies

The current studies mainly demonstrate the coumarin based azomethine-clubbed thiazoles synthesis and their in-vitro evaluation for the first time against α-glucosidase. Due to the catalytic role of α-glucosidase, it has become a precise target for the treatment of type diabetes mellitus (T2DM). The high rate of prevalence of diabetes and its associated health related problems led us to scrutinize the anti-diabetic capability of the synthesized thiazole derivatives (6a-6k). The anticipated structures of prepared compounds were confirmed through FT-IR and NMR spectroscopic methods. All the compounds showed several times potent activity than the standard drug, acarbose (IC₅₀ = 873.34 ± 1.67 µM) against α-glucosidase with IC₅₀ values in range of 0.87 ± 0.02-322.61 ± 1.14 µM. The compound 6k displayed the highest anti-diabetic activity (IC₅₀ = 1.88 ± 0.03 µM). Kinetic study revealed that these are competitive inhibitors for α-glucosidase. The mode of binding of the synthesized molecules were further evaluated by molecular docking, which reflects the importance of azomethine group in protein-ligand interaction. The docking scores are complementary with the IC₅₀ values of compounds while the interaction pattern of the compounds clearly demonstrates their structure-activity relationship. Current study reported medicinal importance of thiazole derivative as future drug candidates for the management of Type 2 Diabetes Mellitus (T2DM).

Phytochemical Composition and Biological Activities of Arctium minus (Hill) Bernh.: A Potential Candidate as Antioxidant, Enzyme Inhibitor, and Cytotoxic Agent

Arctium minus (Hill) Bernh. (Asteraceae), which has a wide distribution area in Turkey, is a medicinally important plant. Eighty percent methanol extracts of the leaf, flower head, and root parts of A. minus were prepared and their sub-fractions were obtained. Spectrophotometric and chromatographic (high-performance liquid chromatography) techniques were used to assess the phytochemical composition. The extracts were evaluated for antioxidant activity by diphenyl-2-picrylhydrazil radical (DPPH^●), 2,2′-Azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS^●+) radical scavenging, and β-carotene linoleic acid bleaching assays. Furthermore, the extracts were subjected to α-amylase, α-glucosidase, lipoxygenase, and tyrosinase enzyme inhibition tests. The cytotoxic effects of extracts were investigated on MCF-7 and MDA-MB-231 breast cancer cell lines. The richest extract in terms of phenolic compounds was identified as the ethyl acetate sub-fraction of the root extract (364.37 ± 7.18 mg_GAE/g_extact). Furthermore, chlorogenic acid (8.855 ± 0.175%) and rutin (8.359 ± 0.125%) were identified as the primary components in the leaves’ ethyl acetate sub-fraction. According to all methods, it was observed that the extracts with the highest antioxidant activity were the flower and leaf ethyl acetate fractions. Additionally, ABTS radical scavenging activity of roots’ ethyl acetate sub-fraction (2.51 ± 0.09 mmol/L Trolox) was observed to be as effective as that of flower and leaf ethyl acetate fractions at 0.5 mg/mL. In the β-carotene linoleic acid bleaching assay, leaves’ methanol extract showed the highest antioxidant capacity (1422.47 ± 76.85) at 30 min. The enzyme activity data showed that α-glucosidase enzyme inhibition of leaf dichloromethane extract was moderately high, with an 87.12 ± 8.06% inhibition value. Lipoxygenase enzyme inhibition was weakly detected in all sub-fractions. Leaf methanol extract, leaf butanol, and root ethyl acetate sub-fractions showed 99% tyrosinase enzyme inhibition. Finally, it was discovered that dichloromethane extracts of leaves, roots, and flowers had high cytotoxic effects on the MDA-MB-231 cell line, with IC50 values of 21.39 ± 2.43, 13.41 ± 2.37, and 10.80 ± 1.26 µg/mL, respectively. The evaluation of the plant extracts in terms of several bioactivity tests revealed extremely positive outcomes. The data of this study, in which all parts of the plant were investigated in detail for the first time, offer promising results for future research.

Bridging the Chemical Profile and Biomedical Effects of Scutellaria edelbergii Essential Oils

The present study explored chemical constituents of Scutellaria edelbergii essential oils (SEEO) for the first time, extracted through hydro-distillation, and screened them against the microbes and free radicals scavenging effect, pain-relieving, and anti-inflammatory potential employing standard techniques. The SEEO ingredients were noticed via Gas Chromatography-Mass-Spectrometry (GC-MS) analysis and presented fifty-two bioactive compounds contributed (89.52%) with dominant volatile constituent; 3-oxomanoyl oxide (10.09%), 24-norursa-3,12-diene (8.05%), and methyl 7-abieten-18-oate (7.02%). The MTT assay via 96 well-plate and agar-well diffusion techniques against various microbes was determined for minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), IC₅₀, and zone of inhibitions (ZOIs). The SEEO indicated considerable antimicrobial significance against tested bacterial strains viz. Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Enterococcus faecalis and the fungal strains Fusarium oxysporum and Candida albicans. The free radicals scavenging potential was noticed to be significant in 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) as compared to 2,2′-azino-bis-3-ethylbenzotiazolin-6-sulfonic acid (ABTS) assays with IC₅₀ = 125.0 ± 0.19 µg/mL and IC₅₀ = 153.0 ± 0.31 µg/mL correspondingly; similarly, the antioxidant standard in the DPPH assay was found efficient as compared to ABTS assay. The SEEO also offered an appreciable analgesic significance and presented 54.71% in comparison with standard aspirin, 64.49% reduction in writhes, and an anti-inflammatory potential of 64.13%, as compared to the standard diclofenac sodium inhibition of 71.72%. The SEEO contain bioactive volatile ingredients with antimicrobial, free radical scavenging, pain, and inflammation relieving potentials. Computational analysis validated the anti-inflammatory potential of selected hit “methyl 7-abieten-18-oate” as a COX-2 enzyme inhibitor. Docking results were very good in terms of docked score (−7.8704 kcal/mol) and binding interactions with the functional residues; furthermore, MD simulation for 100 ns has presented a correlation with docking results with minor fluctuations. In silico, ADMET characteristics supported that methyl 7-abieten-18-oate could be recommended for further investigations in clinical tests and could prove its medicinal status as an anti-inflammatory drug.