Screening of Panamanian Plants for Cosmetic Properties, and HPLC-Based Identification of Constituents with Antioxidant and UV-B Protecting Activities

Chemo- and regio-selective enzymatic lipophilisation of rutin, and physicochemical and antioxidant properties of rutin ester derivatives

Enzymes are one of the most powerful tools in organic Green Chemistry and enzymatic reactions offer numerous advantages like regio- and enantio-selectivity along with their eco-friendly and sustainable nature. More specifically, lipases can catalyse both ester hydrolysis and formation depending on the nature of the substrate and water content. Herein, the focus is on the development of an enzymatically catalysed lipophilisation of natural compounds using lipases of microbial origin and the investigation of the optimal reaction conditions, aiming ultimately to ameliorate the compounds' properties. The flavonoid disaccharide rutin (quercetin-3-O-rutinoside) was the model compound on which the acylation protocol was built, allowing an efficient procedure to be established, while simultaneously offering the possibility of developing rapid, clear and robust methodologies, using state-of-the-art techniques, for analysis and purification of the synthesized compounds. An optimal 72 h reaction at 55 °C, using Candida antarctica lipase B immobilized on acrylic resin, combined with silicon dioxide as dehydrating agent, followed by product purification, achieved conversion ratios up to 50%. Full characterization and evaluation of the physicochemical and antioxidant properties of the esterified compounds was obtained. The lipophilicity of the rutin esters produced increased with increasing alkyl chain length, yet antioxidant properties were unaffected in comparison with the parent compound. A preparatively useful acylation protocol was established, allowing full investigation into the properties of the acylated compounds. It is also applicable for use on mixtures of compounds as most natural products are found in nature in mixtures and such a development greatly enhances the potential of this method for future commercial applications.

Phytochemical Study and In Vitro Screening Focusing on the Anti-Aging Features of Various Plants of the Greek Flora

Skin health is heavily affected by ultraviolet irradiation from the sun. In addition, senile skin is characterized by major changes in the collagen, elastin and in the hyaluronan content. Natural products (NPs) have been shown to delay cellular senescence or in vivo aging by regulating age-related signaling pathways. Moreover, NPs are a preferable source of photoprotective agents and have been proven to be useful against the undesirable skin hyperpigmentation. Greek flora harvests great plant diversity with approximately 6000 plant species, as it has a wealth of NPs. Here, we report an extensive screening among hundreds of plant species. More than 440 plant species and subspecies were selected and evaluated. The extracts were screened for their antioxidant and anti-melanogenic properties, while the most promising were further subjected to various in vitro and cell-based assays related to skin aging. In parallel, their chemical profile was analyzed with High-Performance Thin-Layer Chromatography (HPTLC) and/or Ultra-Performance Liquid Chromatography High-Resolution Mass Spectrometry (UPLC-HRMS). A variety of extracts were identified that can be of great value for the cosmetic industry, since they combine antioxidant, photoprotective, anti-melanogenic and anti-aging properties. In particular, the methanolic extracts of Sideritis scardica and Rosa damascena could be worthy of further attention, since they showed interesting chemical profiles and promising properties against specific targets involved in skin aging.

Bioactive Metabolites of the Stem Bark of Strychnos aff. darienensisand Evaluation of Their Antioxidant and UV Protection Activity in Human Skin Cell Cultures

The genus Strychnos (Loganiaceae) is well-known as a rich source of various bioactive metabolites. In continuation of our phytochemical studies on plants from Amazonia, we examined Strychnosaff. darienensis, collected in Peru. This species has been traditionally used in South America and is still presently used as a drug by the Yanesha tribe in Peru. Phytochemical investigation of this plant led to the isolation and structure elucidation by ΝuclearΜagnetic Resonance and High Resolution Mass Spectroscopy of 14 compounds that belong to the categories of phenolic acids [p-hydroxybenzoic acid (1) and vanillic acid (2)], flavonoids [luteolin, (3),3-O-methyl quercetin (4), strychnobiflavone (5), minaxin (6) and 3’,4’,7-trihydroxy-flavone (7)], lignans [syringaresinol-β-D-glucoside (8), balanophonin (9) and ficusal (10)] and alkaloids [venoterpine (11), 11-methoxyhenningsamine (12), diaboline (13) and 11-methoxy diaboline (14)]. The isolated flavonoids—a class known for its anti-aging activities—were further evaluated for their biological activities on normal human skin fibroblasts. Among them, only (6), and to a lesser extent (7), exhibited cytotoxicity at 100 µg/ml. All five flavonoids suppressed intracellularreactive oxygen species (ROS) levels, either basal or following stimulation with hydrogen peroxide or both. Moreover, luteolin and strychnobiflavone protected skin fibroblasts against ultraviolet (UV)-irradiation-induced cell death. The isolated flavonoids could prove useful bioactive ingredients in the cosmetic industry.

Integrated HPTLC-based Methodology for the Tracing of Bioactive Compounds in Herbal Extracts Employing Multivariate Chemometrics. A Case Study on Morus alba

INTRODUCTION

In drug discovery, bioassay-guided isolation is a well-established procedure, and still the basic approach for the discovery of natural products with desired biological properties. However, in these procedures, the most laborious and time-consuming step is the isolation of the bioactive constituents. A prior identification of the compounds that contribute to the demonstrated activity of the fractions would enable the selection of proper chromatographic techniques and lead to targeted isolation.

OBJECTIVE

The development of an integrated HPTLC-based methodology for the rapid tracing of the bioactive compounds during bioassay-guided processes, using multivariate statistics. Materials and Methods - The methanol extract of Morus alba was fractionated employing CPC. Subsequently, fractions were assayed for tyrosinase inhibition and analyzed with HPTLC. PLS-R algorithm was performed in order to correlate the analytical data with the biological response of the fractions and identify the compounds with the highest contribution. Two methodologies were developed for the generation of the dataset; one based on manual peak picking and the second based on chromatogram binning. Results and Discussion - Both methodologies afforded comparable results and were able to trace the bioactive constituents (e.g. oxyresveratrol, trans-dihydromorin, 2,4,3'-trihydroxydihydrostilbene). The suggested compounds were compared in terms of R_f values and UV spectra with compounds isolated from M. alba using typical bioassay-guided process.

CONCLUSION

Chemometric tools supported the development of a novel HPTLC-based methodology for the tracing of tyrosinase inhibitors in M. alba extract. All steps of the experimental procedure implemented techniques that afford essential key elements for application in high-throughput screening procedures for drug discovery purposes. Copyright © 2017 John Wiley & Sons, Ltd.

Optimized synthesis of novel prenyl ferulate performed by feruloyl esterases from Myceliophthora thermophila in microemulsions

Five feruloyl esterases (FAEs; EC 3.1.1.73), FaeA1, FaeA2, FaeB1, and FaeB2 from Myceliophthora thermophila C1 and MtFae1a from M. thermophila ATCC 42464, were tested for their ability to catalyze the transesterification of vinyl ferulate (VFA) with prenol in detergentless microemulsions. Reaction conditions were optimized investigating parameters such as the medium composition, the substrate concentration, the enzyme load, the pH, the temperature, and agitation. FaeB2 offered the highest transesterification yield (71.5 ± 0.2%) after 24 h of incubation at 30 °C using 60 mM VFA, 1 M prenol, and 0.02 mg FAE/mL in a mixture comprising of 53.4:43.4:3.2 v/v/v n-hexane:t-butanol:100 mM MOPS-NaOH, pH 6.0. At these conditions, the competitive side hydrolysis of VFA was 4.7-fold minimized. The ability of prenyl ferulate (PFA) and its corresponding ferulic acid (FA) to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals was significant and similar (IC₅₀ 423.39 μM for PFA, 329.9 μM for FA). PFA was not cytotoxic at 0.8-100 μM (IC₅₀ 220.23 μM) and reduced intracellular reactive oxygen species (ROS) in human skin fibroblasts at concentrations ranging between 4 and 20 μM as determined with the dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay.

Chemical constituents from Cordia alliodora and C. colloccoca (Boraginaceae) and their biological activities

Two new natural products, 5-O-[β-D-apiofuranosyl-(1→6)-β-d-glucopyranosyl]-1-isoindolinone (1) as well as N-(2E)-3-[(2S,3R)-2-(4-hydroxy-3-methoxyphenyl)-3-(hydroxymethyl)-7-methoxy-2,3-dihydro-1-benzofuran-5-yl]acryloylglycine (2), along with four known compounds (3-6), were isolated from the methanolic extract of Cordia alliodora root bark. Furthermore, the methanolic extract of Cordia colloccoca leaves, afforded the known flavonoids afzelin (7) and quercitrin (8). The isolated secondary metabolites were assayed for their antimicrobial activities against a panel of 6g positive and negative bacteria and three human pathogenic fungi. Moreover, their antiproliferative effect was also evaluated in vitro against the human non-small-cell bronchopulmonary carcinoma line NSCLC-N6, the epidermoid lung cancer cell line A549 as well as the normal human skin fibroblast cell line (AG01523).