Physicochemical Properties of Choline Chloride-Based Natural Deep Eutectic Solvents (NaDES) and Their Applicability for Extracting Oil Palm Flavonoids

Oil palm (Elaeis guineensis Jacq.) leaf (OPL) is abundantly generated from oil palm plantations as biomass that is rich in bioactive metabolites, primarily flavonoids. Six natural deep eutectic solvents (NaDES) were synthesized using a direct heating technique from different combinations of choline chloride with 1,2-propanediol (PD), 1,4-butanediol (BD), glycerol (GLY), glucose (GLU), maltose (MAL) and lactic acid (LA). The synthesized NaDES were subjected to physicochemical and biological evaluations comprising physical appearance, density, water activity, viscosity, polarity, thermal behaviors, spectroscopic analysis, cytotoxicity, radical scavenging activities and solubility tests. Compared to aqueous methanol, the synthesized NaDES, which appeared as a slightly to moderately viscous transparent liquid, showed favorable physicochemical properties as extraction solvents with a low cytotoxicity profile on cultured fibroblast cells. Further, the NaDES obtained from the choline chloride:lactic acid (LA) combination showed high free radical scavenging characteristics. Hydrogen bonding interactions were shown to play a significant role in the formation of the NaDES. Further, ultra-high-performance liquid chromatography ultraviolet/photodiode array (UHPLC-UV/PDA) analysis revealed that the NaDES from the choline chloride:glycerol (GLY) combination had comparable efficiencies with aqueous methanol regarding extracting flavonoids (luteolin and apigenin derivatives) from OPLs. The results of the present study suggested that the tailor-made NaDES were not only easy-to-use, stable and safe solvents but also suitable for extracting bioactive phytochemical compounds. The study highlighted their potential as an alternative green technology for applications in oil palm biomass utilization programs.

Formulation and evaluation of wound healing activity of Elaeis guineensis Jacq leaves in a Staphylococcus aureus infected Sprague Dawley rat model

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants are crucial to healing numerous illnesses. Elaeis guineensis Jacq (family Arecaceae) is a medicinal plant traditionally used for the treatment of wounds.

AIM OF THE STUDY

However, there are no scientific reports documented on the wound healing activities of this plant against Staphylococcus aureus infections in the Sprague Dawley male rat model. Thus, the present study was conducted to evaluate the wound healing potential of E. guineensis extract leaves.

MATERIALS AND METHODS

The crude extract was prepared in 10% (w/w) ointment and evaluated for wound healing activity using excision and infected wound models in Sprague Dawley rats. The wound healing activity was evaluated from wound closure rate, CFU reduction, histological analysis of granulation tissue and matrix metalloprotease expression.

RESULTS

The results show that the E. guineensis extract has potent wound healing ability, as manifest from improved wound closure and tissue regeneration supported by histopathological parameters. Assessment of granulation tissue every fourth day showed a significant reduction in the microbial count. The expression of matrix metalloproteinases was well correlated with the other results, hence confirming E. guineensis wound healing activity's effectiveness.

CONCLUSIONS

E. guineensis enhanced infected wound healing in rats, thus supporting its traditional use.

Insights on the Extraction Performance of Alkanediols and Glycerol: Using Juglans regia L. Leaves as a Source of Bioactive Compounds

Glycerol and alkanediols are being studied as alternative solvents to extract phytochemicals from plant material, often as hydrogen bond donors in deep eutectic solvents (DESs). Many of those alcohols are liquid at room temperature, yet studies of their use as extraction solvents are scarce. In this work, glycerol and a series of alkanediols (1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, and 1,2-hexanediol) were studied for the extraction of phenolic compounds from Juglans regia L. leaves, a rich source of this class of bioactive compounds. The extraction yield was quantified, and the bioactivity of both extracts and pure solvents was evaluated by measuring the anti-inflammatory and cytotoxic activities. The solvents showing the best combined results were 1,2 and 1,3-propanediol, as their extracts presented a high amount of phenolic compounds, close to the results of ethanol, and similar cytotoxicity against cervical carcinoma cells, with no impact on non-tumor porcine liver cells in the studied concentration range. On the other hand, none of the extracts (and solvents) presented anti-inflammatory activity. Overall, the results obtained in this work contribute to the study of alternative solvents that could potentially be used also as formulation media, highlighting the importance of walnut leaves as a source of bioactive compounds.