Polymeric nanoparticles for enhanced delivery and improved bioactivity of essential oils.

Essential oils are volatile constituents that give aromatic plants their characteristic odour. The application of these plant actives in food, agriculture, pharmaceutics, and cosmetics has been widely studied. Aromatherapy, a complementary therapy involving the use of essential oils to treat several diseases ranging from microbial infections to metabolic dysfunctions, has been utilised for centuries. Anticancer, antimicrobial, and anti-inflammatory activities are well-established among other pharmacological properties of these aromatic oils. The oils, which are composed mainly of terpene-based compounds, have also been explored as nutraceuticals, alternative green preservatives, and functional additives in foods. However, due to their physicochemical properties, viz high volatility and low aqueous solubility, essential oil delivery to target receptors were challenging when administered as chemotherapeutics. Hence, formulating essential oils with suitable excipients to enhance their delivery and bioavailability, invariably improving their bioactivity and therapeutic efficacy becomes expedient. Nanotechnology presents a unique strategy to develop a particulate delivery system for the controlled, sustained, and extended release of essential oils. In this review, we examine and summarize the trends and developments in the formulation of essential oils using polymeric nanoparticles.

Microencapsulation of eucalyptol in polyethylene glycol and polycaprolactone using particles from gas-saturated solutions.

Eucalyptol is the natural cyclic ether which constitutes the bulk of terpenoids found in essential oils of Eucalyptus spp. and is used in aromatherapy for treatment of migraine, sinusitis, asthma and stress. It acts by inhibiting arachidonic acid metabolism and cytokine production. Chemical instability and volatility of eucalyptol restrict its therapeutic application and necessitate the need to develop an appropriate delivery system to achieve extended release and enhance its bioactivity. However, the synthesis method of the delivery system must be suitable to prevent loss or inactivation of the drug during processing. In this study, supercritical carbon dioxide (scCO2) was explored as an alternative solvent for encapsulation and co-precipitation of eucalyptol with polyethylene glycol (PEG) and/or polycaprolactone (PCL) using the particles from gas-saturated solution (PGSS) process. Polymers and eucalyptol were pre-mixed and then processed in a PGSS autoclave at 45 °C and 80 bar for 1 h. The mixture in scCO2 was micronized and characterized. The presence of eucalyptol in the precipitated particles was confirmed by infrared spectroscopy, gas chromatography and mass spectrometry. The weight ratios of PEG-PCL blends significantly influenced loading capacity and encapsulation efficiency with 77% of eucalyptol encapsulated in a 4 : 1 composite blend of PEG-PCL. The particle size distribution of the PGSS-micronized particles ranged from 30 to 260 µm. ScCO2 assisted microencapsulation in PEG and PCL reduced loss of the volatile drug during a two-hour vaporization study and addition of PCL extended the mean release time in simulated physiological fluids. Free radical scavenging and lipoxygenase inhibitory activities of eucalyptol formulated in the PGSS-micronized particles was sustained. Findings from this study showed that the scCO2-assisted micronization can be used for encapsulation of volatile drugs in polymeric microparticles without affecting bioactivity of the drug.

Antidiabetic Potentials of Citrus aurantifolia Leaf Essential Oil.

Citrus aurantifolia leaf essential oil was extracted via hydrodistillation, chemical composition of the oil was analyzed using gas chromatography-mass spectrometry and its antidiabetic potentials was assessed in alloxan-induced hyperglycaemic rats using metformin as the reference drug for comparison. Chemical analysis showed that D-limonene (57.84%) was the major constituent of the oil. Other notable compounds identified were neral (7.81%), linalool (4.75%), sulcatone (3.48%) and isogeraniol (3.48%). Intraperitoneal administration of C. aurantifolia oil (100 mg/Kg b.wt.) to hyperglycaemic rats for 14 days caused significant reduction in fasting blood and hepatic glucose, whereas hepatic concentration of glycogen was significantly increased. Also, improvement in dyslipidaemia was observed in C. aurantifolia essential oil-treated hyperglycaemic rats; serum concentration of total cholesterol, triacylglycerol and low density lipoprotein-cholesterol were significantly reduced and high density lipoprotein-cholesterol was increased, resulting in decreased predisposition of rats to cardiac risks. Antihyperglycaemic potential of administration of the oil was lower but compared favourably with the oral antihyperglycaemic agent used as reference antidiabetic drug. Overall, data from this study showed that essential oil from the leaf of C. aurantifolia grown in North-Central Nigeria is a D-limonene chemotype. The oil showed considerable glucose lowering effect as well as the potential to ameliorate hyperglycaemia-induced dyslipidaemic complications in alloxanized rats.

Antioxidant and alpha-amylase inhibitory potentials of Cocos nucifera husk.

Concoctions containing extract from Cocos nucifera husk fiber are used in Nigeria by traditional medicine practitioners for management of diabetes and its associated complications. Preliminary antidiabetic study was designed to validate the folkloric usage of the plant extract. Dried coconut husk fiber was pulverized and extracted with methanol, followed by partitioning of the methanolic extract in ethyl acetate. Phenolic content, radical scavenging activity and antioxidant capacity as well as inhibitory effects of C. nucifera methanolic (CN-M) extract and its ethyl acetate (CN-E) fraction on pancreatic α-amylase and lipid peroxidation were determined. Total phenolic content and antioxidant capacity of CN-E fraction were significantly higher than that of CN-M extract, whereas there was no significant difference in their ability to scavenge free radicals. The CN-E fraction also exhibited higher in vitro and in vivo inhibitory effects on α-amylase activity and lipid peroxidation; reducing blood glucose level within 5 days following intraperitoneal administration of the C. nucifera extract to alloxan-induced hyperglycemic rats. The phenolic-rich extracts from coconut husk can be further explored as nutraceutical supplement in food formulation for diabetic patients.

Antidiabetic potentials of essential oil extracted from the leaves of Hoslundia opposita Vahl.

This study was aimed at assessing the potential of essential oil from the leaf of Hoslundia opposita in the treatment of diabetes. Forty-eight rats (Rattus norvegicus) were randomized into two groups; nondiabetic and diabetic groups, each with four subgroups. Animals in the diabetic group were induced with diabetes using a single dose of alloxan monohydrate, 160 mg/kg body weight (b. wt.). The rats were treated with 110 and 220 mg/kg b. wt. of the essential oil. All treatments were administered, intraperitoneally, once a day for 4 days. In the nondiabetic condition, there was no effect of the oil on fasting blood glucose (FBG) levels in rats. In diabetic rats, the oil caused a significant reduction in FBG levels. Treatment with 110 mg/kg b. wt. of the oil reduced FBG almost to the normoglycemic level by day 4 and the overall glucose excursion during a 3-h intraperitoneal glucose tolerance test approached the baseline level at 120 min. Also, hepatic glycogen was significantly higher, while the glucose concentrations were lower in the diabetic-treated group when compared with the diabetic untreated group. Histological examinations revealed a mildly distorted architecture of the pancreatic islets ß-cells of diabetic rats treated with the oil, while those of the untreated rats were severely degenerated. Overall, the in vivo antihyperglycemic activity of the essential oil may prove to be of clinical importance in the management of type 2 diabetes.