Perillaldehyde-Loaded Lipid Nanoformulations: Formulation,Pharmacokinetic And Pharmacological Evaluations

The growing popularity of natural medicines continues to rise within the health care delivery system as the threat posed by diabetes and other cardiovascular diseases increases. Natural bioactive compounds obtained from plant sources have been used globally since ancient times, and have gained recognition among physicians and patients for their better therapeutic value and fewer adverse effects as compared with modern medicines. To date, plants have served as one of the major sources of drugs and remain the future of global health, especially with the advancement of combinatorial chemistry and high throughput screening techniques. Several natural-based bioactive compounds have also been proven to possess wide range of pharmacological properties which could serve as multi-target approach toward the management of diabetes(a major risk factor for metabolic syndrome), dyslipidemia and other cardiovascular diseases. However, over 40% of the prospective wealth of new chemical entities is characterized by high lipophilicity which has ultimately reflected in poor water solubility and erratic absorption as well as limited bioavailability, causing a range of medication control problems, such as insufficient dosing, high intra- and inter-subject variability, extensive first pass hepatic metabolism, and poor therapeutic outcomes. The natural bioactive substance(perillaldehyde), from the essential oil accumulating plant(Perilla frutescens), is a new perspective medicinal compound. Its several biological and pharmacological properties, including anti-inflammatory, anti-allergic, antitumor, antioxidant, anticarcinogenic, vasodilation and neuroprotective effects, project it as an ideal compound which could have combined therapeutic outcomes. However, these functional and medicinal applications of perillaldehyde seem to be hampered by the strong odour(flavour), poor water solvation and the lack of novel delivery systems. Moreover, the possible pharmacological activities in the management of metabolic disorders such as diabetes and hyperlipidemia by this compound are yet to be ascertained. Thus, the demand for more scientific approaches to design and deliver natural bioactive substances such as perillaldehyde in an acceptable manner, to increase patient compliance has become imperative in the pharmaceutical industry. In this regard, the present study seeks to improve the pharmacological applications of perillaldehyde via novel drug delivery systems while investigating its hypoglycaemic and anti-hyperlipidemic prospects in the management of diabetes and related hyperlipidemia. There are five major areas of contribution which have been detailed as follows:Chapter 1 Review of natural bioactive compounds and application of novel drug delivery systems This section provides a review of related literature on some keywords of the study to wit natural bioactive substances, perillaldehyde(PAH) and novel drug delivery systems. A brief overview of natural bioactive substances as potential sources of drugs for the management of several diseased conditions, especially diabetes and its related complications such as hyperlipidemia was highlighted. The source, physicochemical and the current pharmacological research status as well as limitations and future prospects of perillaldehyde were also duly discussed, to justify the design of this study. The possibility of future successes with the application of novel drug delivery systems towards enhanced activities of bioactive compounds was further outlined. Chapter 2 Perillaldehyde-loaded lipid nanoformulations: Preparations, optimization and characterization This chapter reports the successful preparation of three novel perillaldehyde-loaded lipid nanoformulations viz self nanoemulsifying delivery system(PAH-SNEDS), PAH-SNEDS pellets and liposomal nanoformulation(PAH-LNF). Using D-optimal experimental design, a three component PAH-SNEDS consisting 40% w/w drug-oil phase, X1(a mixture of perillaldehydeisopropyl myristate/medium chain triglyceride, 1:1, w/w); 48% Surfactant, X2(Kolliphor EL); and 12% co-surfactant, X3(PEG 200), was optimized. A quadratic model(y = 4.85 A + 3.96 B + 0.055 AB – 4.34A2– 0.19B2 + 94.30 where y, A, and B refers to the encapsulation efficiency, ratio of phospholipid to cholesterol and mass of PAH, respectively) was also used to optimize PAHLNF(12 mg/ml). Spherical and homogenous droplets with mean size, polydispersity index(PDI) and zeta potential of 32.8 ± 0.1 nm, 0.270 ± 0.029 and-10.14 ± 0.66 m V, respectively were observed for PAH-SNEDS while a relatively larger droplet size(135.3 ± 0.3 nm), narrower PDI(0.216 ± 0.110) and a more stable zeta potential(-49.9 ± 0.2 m V), was obtained for the unilamellar vesicles of PAH-LNF. PAH-SNEDS and PAH-LNF demonstrated significant increases in dissolution in vitro compared to the free PAH.(Full meaning first) Microcrystalline cellulose(MCC)-based PAH-SNEDS pellets with 10% Kollidon CL was also identified as an ideal solid nanoformulation for PAH. The release mechanism of the pellets best fitted the RitgerPeppas model.Chapter 3 Oral bioavailability and anti-hyperlipidemic potential of Perillaldehydeloaded self nanoemulsifying delivery system in high-fat diet induced hyperlipidemia This unit reports the oral bioavailability and anti-hyperlipidemic investigations of perillaldehydeloaded self-nanoemulsifying delivery system(PAH-SNEDS) in high-fat diet induced hyperlipidemic mice. PAH-SNEDS compared to the unformulated PAH, significantly improved the oral bioavailability by 206.18% in vivo which suggested a promising formulation design for potential liquid bioactive compounds. The oral administration of PAH-SNEDS(240 mg/kg per body weight) in high-fat induced hyperlipidemic mice, also significantly decreased serum total cholesterol(TC), triglyceride(TG) and low-density lipoprotein cholesterol(LDL-C) while increasing high-density lipoprotein cholesterol(HDL-C) level. The improved bioavailability and functional application of PAH via self- nanoemulsifying delivery system suggested a suitable approach to promote its potential anti-hyperlipidemic property. Perillaldehyde(PAH), therefore, promises to be a useful bioactive compound to prevent high-fat diet induced hyperlipidemia. Chapter 4 Tissue distribution and anti-hyperlipidemic activity of perillaldehyde liposomal nanoformulation in Poloxamer-407 induced hyperlipidemia. An optimized PAH-LNF was successfully applied to improve the pharmacological effect of PAH in poloxamer 407-induced hyperlipidemia. Oral administration of PAH-LNF(240 mg/kg per body weight) in rats significantly enhanced solubility and relative bioavailability(270.7%) compared to the free PAH with about 2.7-, 1.5-, 1.3-, 1.3-, and 1.5-fold increase in AUC, T1/2,MRT, C max and T max, respectively. Tissue distribution study also revealed the accumulation of PAH in the liver, lungs, spleen, kidney, brain and heart in order of decreasing affinity. Moreover, a significant decrease in serum total cholesterol(TC), triglyceride(TG) and low-density lipoprotein cholesterol(LDL-C) with simultaneous increase in high-density lipoprotein cholesterol(HDL-C) level was observed in the chemically-induced hyperlipidemic mice which further confirmed PAH’s potential anti-hyperlipidemic properties. PAH-LNF also significantly increased the activities of superoxide dismutase(SOD) and glutathione peroxidase(GSH-Px) with a concurrent decrease in malondialdehyde(MDA) to affirm the antioxidant and hepatoprotective effects of PAH. Thus, liposomal nanoformulation promises to be a useful drug delivery system for the development and wide pharmacological applications of PAH.Chapter 5 In situ intestinal perfusion, anti-hyperglycemic, antioxidant and antiinflammatory investigations of PAH-SNEDS in alloxan-induced diabetes This study reports for the first time the potential anti-hyperglycaemic effect and in situ intestinal perfusion of perillaldehyde developed via self-nanoemulsifying delivery system(PAH-SNEDS). Diabetes was induced in rats by a single intraperitoneal injection of alloxan monohydrate(120 mg/kg body weight) dissolved in freshly prepared sterile 0.9% normal saline. Low, medium and high doses of PAH-SNEDS(60, 120 and 240 mg/kg b.w. of PAH equivalent) were administered daily for 21 days while metformin(230 mg/kg b.w.) a standard antidiabetic drug, served as positive control. A high dose(240 mg/kg) of the free PAH, suspended in sodium carboxymethylcellulose Na CMC(0.5% w/w), was used for comparison. Fasting blood glucose, serum lipid profile, oxidative stress as well as inflammatory biomarkers were assessed to establish the hypoglycaemic potential and other improved pharmacological effects of PAH. The PAH-SNEDS significantly reduced fasting blood glucose levels, increased antioxidant and antiinflammation biomarkers with pronounced anti-hyperlipidemic effect, similar to the positive control. Treatment with the unformulated drug, relative to the high dose of PAH-SNEDS, was significantly lower, which suggested an improved formulation. Additionally, in situ intestinal perfusion study revealed that the absorption and adsorption of PAH was generally high across the intestinal lumen due to the essential oil nature of PAH but was significantly enhanced with PAHSNEDS than the unformulated PAH. Perillaldehyde, therefore, promises to be a potential bioactive compound in the management of diabetes and its complications such as hyperlipidemia.