LC-MS Characterization and Biological Activities of Cuban Cultivars of Plectranthus neochilus Schltr

Plectranthus neochilus Schltr. (Lamiaceae) is a plant recently introduced in Cuba. Worldwide, it is an ethnomedicinal alternative for its use against microbial infections, but the Cuban population use the extracts to treat sleep disorders. To address this apparent incongruity, four collections (from different seasonal conditions in the year) of Cuban P. neochilus cultivars were analyzed in terms of their pharmacognostic characteristics. Three extracts using fresh and dried leaves were chemically and biologically characterized. UPLC-DAD-MS/MS analysis was performed to determine their chemical composition, while a panel of nine microorganisms was used to evaluate their antimicrobial activity. Finally, cytotoxic effects of different fractions were measured in three cell lines by the resazurin viability assay. In contrast to previously reported micro and macromorphological properties of P. neochilus, the leaves from the Cuban cultivars did not present glandular trichomes, nor did they produce quantifiable levels of essential oils. Moreover, aqueous extracts used by the population revealed no significant antimicrobial activity and were not cytotoxic. The three extracts showed a similar phytochemical composition, i.e., eight flavonoids, seven abietane diterpenes, and rosmarinic acid as the major constituent, most of them reported for the first time in this species. The low yield of essential oil, the absence of glandular trichomes, compounds with a high level of oxidation, and a moderate antimicrobial activity detected were the most distinctive pharmacognostic and biological characteristics of P. neochilus grown in Cuba. These aspects could explain its non-use as an antimicrobial.

Abietane Diterpenes of the Genus Plectranthus Sensu Lato

Plectranthus (Lamiaceae), which—according to the latest systematic revision—includes three separate genera (Coleus, Plectranthus sensu stricto, and Equilabium), is a genus widely used in traditional medicine—mainly in the treatment of various ailments of the digestive tract, respiratory tract, and skin. Many species of Plectranthus s.l. have been shown to produce phenolic compounds and terpenes. Diterpenes, especially those of the abietane class, are the most studied group of secondary metabolites found in Plectranthus s.l., which is characterized by a significant structural diversity arising from the oxygenation and further rearrangement of the basic tricyclic abietane skeleton to a complete aromatization of the ring system. This review summarizes the known information on abietane diterpenes, showing their structures, sources, and biosynthesis. A classification of these compounds into nine groups, according to the arrangement of their ring C, is used. Royleanones, spirocoleons, and hydroquinones are the largest classes of abietane diterpenes, covering more than 70% of all the compounds reviewed.

Self-Assembly Nanoparticles of Natural Bioactive Abietane Diterpenes

Different approaches have been reported to enhance penetration of small drugs through physiological barriers; among them is the self-assembly drug conjugates preparation that shows to be a promising approach to improve activity and penetration, as well as to reduce side effects. In recent years, the use of drug-conjugates, usually obtained by covalent coupling of a drug with biocompatible lipid moieties to form nanoparticles, has gained considerable attention. Natural products isolated from plants have been a successful source of potential drug leads with unique structural diversity. In the present work three molecules derived from natural products were employed as lead molecules for the synthesis of self-assembled nanoparticles. The first molecule is the cytotoxic royleanone 7α-acetoxy-6β-hydroxyroyleanone (Roy, 1) that has been isolated from hairy coleus (Plectranthus hadiensis (Forssk.) Schweinf). ex Sprenger leaves in a large amount. This royleanone, its hemisynthetic derivative 7α-acetoxy-6β-hydroxy-12-benzoyloxyroyleanone (12BzRoy, 2) and 6,7-dehydroroyleanone (DHR, 3), isolated from the essential oil of thicket coleus (P. madagascariensis (Pers.) Benth.) were employed in this study. The royleanones were conjugated with squalene (sq), oleic acid (OA), and/or 1-bromododecane (BD) self-assembly inducers. Roy-OA, DHR-sq, and 12BzRoy-sq conjugates were successfully synthesized and characterized. The cytotoxic effect of DHR-sq was previously assessed on three human cell lines: NCI-H460 (IC50 74.0 ± 2.2 µM), NCI-H460/R (IC50 147.3 ± 3.7 µM), and MRC-5 (IC50 127.3 ± 7.3 µM), and in this work Roy-OA NPs was assayed against Vero-E6 cells at different concentrations (0.05, 0.1, and 0.2 mg/mL). The cytotoxicity of DHR-sq NPs was lower when compared with DHR alone in these cell lines: NCI-H460 (IC50 10.3 ± 0.5 µM), NCI-H460/R (IC50 10.6 ± 0.4 µM), and MRC-5 (IC5016.9 ± 0.5 µM). The same results were observed with Roy-OA NPs against Vero-E6 cells as was found to be less cytotoxic than Roy alone in all the concentrations tested. From the obtained DLS results, 12BzRoy-sq assemblies were not in the nano range, although Roy-OA NP assemblies show a promising size (509.33 nm), Pdl (0.249), zeta potential (−46.2 mV), and spherical morphology from SEM. In addition, these NPs had a low release of Roy at physiological pH 7.4 after 24 h. These results suggest the nano assemblies can act as prodrugs for the release of cytotoxic lead molecules.

Di- and Triterpenoids Isolation and LC-MS Analysis of Salvia marashica Extracts with Bioactivity Studies

In this study, dichloromethane, acetone, and methanol extracts of the aerial parts of the Salvia marashica plant which is an endemic species to Anatolia, were investigated. The total phenolic amounts of these extracts were determined as pyrocatechol equivalent and total flavonoids as quercetin equivalent. Antioxidant activity was determined by four complementary methods including inhibition of lipid peroxidation (by β-carotene color expression), DPPH free radical scavenging activity, ABTS cation radical scavenging activity and CUPRAC methods. Anticholinesterase activity of the extracts was investigated by the Ellman method against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. Viability and cytotoxic activity tests were carried out on the fibroblast L929 cells and cytotoxic A549 lung cancer cells, respectively. The triterpenoids and diterpenoids constitute the major secondary metabolites of the S. marashica acetone and methanol extracts isolated by chromatographic methods. Their structures were determined based on spectroscopic methods, namely NMR and mass analyses. Ten terpenoids were obtained from either acetone or methanol extracts of the S. marashica. Seven of them were triterpenoids, elucidated as lupeol, lupeol-3-acetate, lup-12, 20(29)-diene, lup-20(29)-ene, α-amyrin-tetracosanoate, oleanolic acid and ursolic acid besides a steroid β-sitosterol. Two abietane diterpenes, abieta-8,11,13-triene (1) and 18-acetoxymethylene-abieta-8,11,13-triene (2), were obtained from the acetone extract which were isolated from a Salvia species for the first time in the present study. The methanol extract was found to be very rich in rosmarinic acid determined by LC-MS/MS analysis.

Membrane-Mediated Sars-cov-2 Host Cell Entry: Potential Inhibitory Roles of Terpenoids in Silico

Targeting viral cell entry proteins is an emerging therapeutic strategy for inhibiting the first stage of SARS-CoV-2 infection. In this study, 106 bioactive terpenoids from African medicinal plants were screened through molecular docking analysis against human angiotensin-converting enzyme 2 (hACE2), human transmembrane protease serine 2 (TMPRSS2) and the S proteins of SARS-CoV-2, SARS-CoV and MERS-CoV. In silico ADMET and drug-likeness prediction, molecular dynamics simulation (MDS), binding free energy calculations and clustering analysis of MDS trajectories were performed on the top docked compounds to respective targets. The results revealed eight terpenoids with high binding tendencies to the catalytic residues of different targets. Pentacyclic terpenoids: 24-methylene cycloartenol and isoiguesterin interacted with the hACE2 binding hotspots for the SARS-CoV-2 Spike protein. 11-hydroxy-2 - (3,4-dihydroxybenzoyloxy) abieta -5,7,9 (11),13-tetraene-12-one, 11-hydroxy-2 -(4-hydroxybenzoyloxy)-abieta- 5,7,9(11),13-tetraene-12-one and other abietane diterpenes interacted strongly with the S1-specificy pocket of TMPRSS2. 3-benzoylhosloppone and cucurbitacin interacted with the RBD and S2 subunit of SARS-CoV-2 spike protein respectively. The predicted druggable and ADMET favourable terpenoids formed structurally stable complexes in the simulated dynamics environment. These terpenoids provides core structure that can be exploited for further lead optimization to design drugs against SARS-CoV-2 cell mediated entry, subject to further in vitro and in vivo studies.

Alpha-Glucosidase and Alpha-Amylase Inhibitory Activities, Molecular Docking, and Antioxidant Capacities of Salvia aurita Constituents

Diabetes mellitus (DM) is one of the most dangerous metabolic diseases with a high rate of mortality worldwide. It is well known that insulin resistance and deficiency in insulin production from pancreatic β-cells are the main characteristics of DM. Due to the detrimental side effects of the current treatment, there is a considerable need to develop new effective antidiabetic drugs, especially alpha-glucosidase and alpha-amylase inhibitors with lesser adverse effects. These inhibitors are known to be directly involved in the delay of carbohydrate digestion, resulting in a reduction of glucose absorption rate and, consequently, reducing the postprandial rise of plasma glucose, which can reduce the risk of long-term diabetes complications. Furthermore, natural products are well-known sources for the discovery of new bioactive compounds that can serve as scaffolds for drug discovery, including that of new antidiabetic drugs. The phytochemical investigation of Salvia aurita collected from Hogobach Pass, Eastern Cape Province, South Africa (SA), yielded four known abietane diterpenes namely carnosol (1), rosmanol (2), 7-methoxyrosmanol (3), 12-methoxycarnosic acid (4), and one flavonoid named 4,7-dimethylapigenin (5). Structural characterization of these isolated compounds was conducted using 1 and 2D NMR, in comparison with reported spectroscopic data. These compounds are reported for the first time from S. aurita. The biological evaluation of the isolated compound against alpha-glucosidase exhibited strong inhibitory activities for 3 and 2 with the half maximal inhibitory concentration (IC50) values of 4.2 ± 0.7 and 16.4 ± 1.1 µg/mL respectively, while 4 and 1 demonstrated strong alpha-amylase inhibitory activity amongst the isolated compounds with IC50 values of 16.2 ± 0.3 and 19.8 ± 1.4 µg/mL. Molecular docking analysis confirms the strong inhibitory activity of 3 against alpha-glucosidase. Additionally, excellent antioxidant capacities were displayed by 2, 1, and 3, respectively, with oxygen radical absorbance capacity (ORAC) (25.79 ± 0.01; 23.96 ± 0.01; 23.94 ± 0.02) mM Trolox equivalent (TE)/g; 1 and 2 as ferric-ion reducing antioxidant power (FRAP) (3.92 ± 0.002; 1.52 ± 0.002) mM ascorbic acid equivalent (AAE)/g; 5 and 2 as Trolox equivalent absorbance capacity (TEAC) (3.19 ± 0.003; 2.06 ± 0.003) mM TE/g. The methanolic extract of S. aurita is a rich source of abietane diterpenes with excellent antioxidant and antidiabetic activities that can be useful to modulate oxidative stress and might possibly be excellent candidates for the management of diabetes. This is the first scientific report on the phytochemical isolation and biological evaluation of the alpha-glucosidase and alpha-amylase inhibitory activities of Salvia aurita.

Alpha-glucosidase and Alpha-amylase Inhibitory Activities, Molecular Docking and Antioxidant Capacities of Salvia Aurita Constituents

Diabetes mellitus (DM) is one of the most dangerous metabolic diseases with high rate of mortality worldwide. It is well known that insulin resistance and deficiency in insulin production from pancreatic β-cells are the main characteristic of DM. Due to the detrimental side effects of the current treatment, there is a considerable need to develop new effective antidiabetic drugs, especially alpha-glucosidase and alpha-amylase inhibitors with lesser adverse effects. These inhibitors are known to be directly involved in the delay of carbohydrate digestion, resulting in a reduction of glucose absorption rate and consequently reduce the post-prandial raise of plasma glucose, which can reduce the risk of long-term diabetes complications. Hence, natural products are well-known sources for the discovery of new scaffold for drugs discovery, including new antidiabetic drugs. The phytochemical investigation of Salvia aurita collected from Hogobach pass, Eastern Cape, South Africa (SA), yielded four known abietane diterpenes namely carnosol (1), rosmanol (2), 7-methoxyrosmanol (3), 12-methoxycarnosic acid (4) and one flavonoid named 4,7-dimethylapigenin (5). Structural characterization of these isolated compounds was conducted using 1 and 2D NMR, in comparison with reported spectroscopic data. These compounds are reported for the first time from S. aurita. The biological evaluation of the isolated compound against alpha-glucosidase exhibited strong inhibitory activities for 3 and 2 with IC50 values of 4.2 ± 0.7 and 16.4 ± 1.1 µg/mL respectively, while 4 and 1 demonstrated strong alpha-amylase inhibitory activity amongst the isolated compounds with IC50 of 16.2 ± 0.3 and 19.8 ± 1.4 µg/mL. Molecular docking analysis confirms strong inhibitory activity of 3 against alpha-glucosidase. Additionally, excellent antioxidant capacities were displayed by 2, 1 and 3 respectively as ORAC (25789.9 ± 10.5; 23961.8 ± 14.1; 23939.3 ± 2.4) µM TE/g; 1 and 2 as FRAP (3917.8 ± 2.1; 1522.3 ± 0.9) µM AAE/g; 5 and 2 as TEAC (3190.4 ± 2.8; 2055.0 ± 2.6) µM TE/g. The methanolic extract of S. aurita is a rich source of abietane diterpenes with excellent antioxidant and anti-diabetic activities that can be useful to modulate oxidative stress, and might possibly be excellent candidates for the management of diabetes. This is the first scientific report on the phytochemical isolation and biological evaluation of alpha-glucosidase and alpha-amylase inhibitory activities of Salvia aurita.