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-6ß-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-6ß-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.

Parvifloron D from Plectranthusstrigosus: Cytotoxicity Screening of Plectranthus spp. Extracts.

The Plectranthus genus is commonly used in traditional medicine due to its potential to treat several illnesses, including bacterial infections and cancer. As such, aiming to screen the antibacterial and cytotoxic activities of extracts, sixteen selected Plectranthus species with medicinal potential were studied. In total, 31 extracts obtained from 16 Plectranthus spp. were tested for their antibacterial and anticancer properties. Well diffusion method was used for preliminary antibacterial screening. The minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of the five most active acetonic extracts (P. aliciae, P. japonicus, P. madagascariensis var. "Lynne", P. stylesii, and P. strigosus) were determined. After preliminary toxicity evaluation on Artemia salina L., their cytotoxic properties were assessed on three human cancer cell lines (HCT116, MCF-7, and H460). These were also selected for mechanism of resistance studies (on NCI-H460/R and DLD1-TxR cells). An identified compound-parvifloron D-was tested in a pair of sensitive and MDR-Multidrug resistance cancer cells (NCI-H460 and NCI-H460/R) and in normal bronchial fibroblasts MRC-5. The chemical composition of the most active extract was studied through high performance liquid chromatography with a diode array detector (HPLC-DAD/UV) and liquid chromatography-mass spectrometry (LC-MS). Overall, P. strigosus acetonic extract showed the strongest antimicrobial and cytotoxic potential that could be explained by the presence of parvifloron D, a highly cytotoxic diterpene. This study provides valuable information on the use of the Plectranthus genus as a source of bioactive compounds, namely P. strigosus with the potential active ingredient the parvifloron D.

Development of a bioadhesive nanoformulation with Glycyrrhiza glabra L. extract against Candida albicans.

Glycyrrhiza glabra L. is considered an important source of bioactive compounds. This study aimed at the development of an efficient solution for the treatment of oral candidiasis. Several extracts of Glycyrrhiza glabra L. were prepared using different solvents and their potential in vitro antifungal activity was assessed. Ethanolic extracts showed the most promising results against C. albicans. This extract was incorporated into mucoadhesive nanoparticles (PLA, PLGA and alginate), which were further included in an oral gel, an oral film and a toothpaste, respectively. The results showed that nanoparticles were successfully produced, presenting a mean size among 100-900 nm with high encapsulation efficiency. In vitro studies showed that the most bioadhesive formulation was the oral film with extract-loaded PLGA nanoparticles, followed by the toothpaste with extract-loaded alginate nanoparticles and the oral gel with extract-loaded PLA nanoparticles.

Antitubercular and anti-inflammatory properties screening of natural products from Plectranthus species.

AIM: Confirm the use of Plectanthus spp. plants in traditional medicine, particularly as anti-inflammatory and anti-infective agents. MATERIALS & METHODS: Compounds previously isolated from Plectranthus spp. were studied for their anti-inflammatory activity using the SNAP assay and RAW 264.7 cells, by the quantification of nitric oxide. An halimane diterpene and its derivatives were tested in infected macrophages with M. tuberculosis H37Rv, using CFU counts assay, at their minimum inhibitory concentration values. Results: The isolated compounds tested at noncytotoxic concentrations, did not reveal nitric oxide scavenging in the S-nitroso-N-acetylpenicillamine and the cellular assays. On the other hand, promising results were obtained regarding one semisynthetic halimane derivative (11R*,13E)-halima-5,13-diene-11,15-diol), previously prepared (2.1 × 105 CFU/mL), with an effect similar to the antitubercular drugs ethambutol (2.0 × 105 CFU/mL) and isoniazid (1.2 × 105 CFU/mL). CONCLUSION: The present report demonstrates the relevance of Plectranthus spp. in medicinal chemistry drug development for TB and other infective respiratory complaints. Also, this work suggests that further studies involving other inflammatory mediators are needed to validate the anti-inflammatory use of these medicinal plants.

Anticancer properties of the abietane diterpene 6,7-dehydroroyleanone obtained by optimized extraction.

AIM: 6,7-dehydroroyleanone (DHR) is a cytotoxic abietane present in the essential oil of Plectranthus madagascariensis. METHODS/RESULTS: Different extraction parameters were tested, and its extraction optimization was accomplished with a Clevenger apparatus-based hydrodistillation. After isolation, its effect on microtubules, P-glycoprotein and caspases was assessed on several cell lines and the compound was coupled with hybrid nanoparticles. The results show that DHR does not interfere with microtubule formation, but evades the resistance mechanisms of P-glycoprotein. Strong activation of caspases-3 and -9 indicates that DHR is able to induce apoptosis by triggering the intrinsic cell death pathway. Moreover, the assembly of DHR with hybrid nanoparticles was able to potentiate the effect of DHR in cancer cells. CONCLUSION: DHR seems to be a promising starting material with anticancer properties to further be explored.

Rosmarinus officinalis L.: an update review of its phytochemistry and biological activity.

The worldwide interest in the use of medicinal plants has been growing, and its beneficial effects being rediscovered for the development of new drugs. Based on their vast ethnopharmacological applications, which inspired current research in drug discovery, natural products can provide new and important leads against various pharmacological targets. This work pioneers an extensive and an updated literature review on the current state of research on Rosmarinus officinalis L., elucidating which compounds and biological activities are the most relevant. Therefore, a search was made in the databases PubMed, ScienceDirect and Web of Science with the terms 'rosemary', 'Rosmarinus officinalis', 'rosmarinic acid' 'carnosol' and 'carnosic acid', which included 286 articles published since 1990 about rosemary's pharmacological activities and their isolated compounds. According to these references, there has been an increasing interest in the therapeutic properties of this plant, regarding carnosic acid, carnosol, rosmarinic acid and the essential oil. The present manuscript provides an updated review upon the most reported activities on R. officinalis and its active constituents.

Extraction Optimization and Structural and Thermal Characterization of the Antimicrobial Abietane 7α-Acetoxy-6ß-hydroxyroyleanone.

The abietane 7α-acetoxy-6ß-hydroxyroyleanone (AHR), obtained from plant extracts, is an attractive lead for drug development, given its known antimicrobial properties. Two basic requirements to establish any compound as a new drug are the development of a convenient extraction process and the characterization of its structural and thermal properties. In this work seven different methods were tested to optimize the extraction of AHR from Plectranthus grandidentatus. Supercritical fluid extraction (SFE) proved to be the method of choice, delivering an amount of AHR (57.351 µg·mg-1) approximately six times higher than the second best method (maceration in acetone; 9.77 µg·mg-1). Single crystal X-ray diffraction analysis of the ARH molecular and crystal structure carried out at 167 ± 2 K and 296 ± 2 K showed only a single phase, here dubbed form III (orthorhombic space group P21212), at those temperatures. The presence of two other polymorphs above room temperature was, however, evidenced by differential scanning calorimetry (DSC). The three forms are enantiotropically related, with the form III → form II and form II → form I transitions occurring at 333.5 ± 1.6 K and 352.0 ± 1.6 K, respectively. The fact that the transitions are reversible suggests that polymorphism is not likely to be an issue in the development pharmaceutical formulations based on ARH. DSC experiments also showed that the compound decomposes on melting at 500.8 ± 0.8 K. Melting should therefore be avoided if, for example, strategies to improve solubility based on the production of glassy materials or solid dispersions are considered.

Naturally Occurring Plectranthus-derived Diterpenes with Antitumoral Activities.

The study of natural sources such as plants, microorganisms and marine organisms has developed interest among the scientific community in recent years for their extensive and diverse chemical composition and consequent biological potential. The search for antitumor compounds is among the lead causes that justify phytochemical studies. Although some natural products have served as FDA approved chemotherapeutic agents, there is still a demand for the search of compounds with those characteristics. The Plectranthus genus has long been used in traditional medicine, and scientific studies have already proven its undeniable value as a source of bioactive compounds. Diterpenes are the most prominent biologically active group of secondary metabolites present in this genus. In particular, abietane diterpenes have long been studied for their biological activities, namely their anti-tumoral potential. In this review, abietane diterpenes isolated from Plectranthus genus with antiproliferative, antitumoral or cytotoxic potential are reported. In addition, a correlation between this subclass of diterpenes with their mechanisms of cell death has been discussed.

Antibacterial, Anti-Inflammatory, Antioxidant, and Antiproliferative Properties of Essential Oils from Hairy and Normal Roots of Leonurus sibiricus L. and Their Chemical Composition.

Essential oils obtained from the NR (normal roots) and HR (hairy roots) of the medicinal plant Leonurus sibiricus root were used in this study. The essential oil compositions were detected by GC-MS. Eighty-five components were identified in total. Seventy components were identified for NR essential oil. The major constituents in NR essential oil were ß-selinene (9.9%), selina-4,7-diene (9.7%), (E)-ß-caryophyllene (7.3%),myli-4(15)-ene (6.4%), and guaia-1(10),11-diene (5.9%). Sixty-seven components were identified in HR essential oil, the main constituents being (E)-ß-caryophyllene (22.6%), and germacrene D (19.8%). The essential oils were tested for cytotoxic effect, antimicrobial, anti-inflammatory, and antioxidant activities. Both essential oils showed activity against grade IV glioma cell lines (IC50 = 400 µg/mL), antimicrobial (MIC and MFC values of 2500 to 125 µg/mL), and anti-inflammatory (decreased level of IL-1ß, IL-6, TNF-α, and IFN-γ in LPS-stimulated cells).The essential oils exhibited moderate antioxidant activity in ABTS (EC50 = 98 and 88 µg/mL) assay. This is the first study to examine composition of the essential oils and their antimicrobial, antioxidant, antiproliferative, and anti-inflammatory activities. The results indicate that essential oils form L. sibiricus root may be used in future as an alternative to synthetic antimicrobial agents with potential application in the food and pharmaceutical industries.