OLEOGELS OF OLIVE OIL AND SOYBEAN OIL FOR TOPICAL DRUG DELIVERY: A COMPARATIVE ANALYSIS

Objective: The objective of the present investigation was to develop olive and soybean oil-based oleogels with Span 40 and/or Tween 80 (as gelator and/or surfactant) and determine the critical gelator concentration (CGC), characterise and compare the rheological, thermal properties and drug release profile of the gels formed for topical delivery. Methods: Olive and soybean oil-based Span 40 and Span 40/Tween 80 oleogel formulations were prepared by solid fiber mechanism and subjected to organoleptic evaluation, FT-IR spectroscopy, thermal analysis, rheological study, kinetic modeling of gelation and drug release. Results: The critical gelator (Span 40) concentration was found to be lower for olive oil (12% w/v) and depend on the type of oil. Tween 80 reduced CGC of soybean oleogels only. Soybean oil-based oleogel containing 18% w/v Span 40 was found to form more flexible, less viscous and thermally less stable formulation with better release of paracetamol as evident from lower melt flow index, Tg value, lower β and higher α value compared to olive oil-based oleogel with 12% w/v Span 40 (CGC). Surfactant addition can be assumed to modify the microarchitecture of the oleogels to a great extent to produce more flexible and thermally stable gels with even better drug release profile. Span-Tween based soybean oleogel formed a gel-matrix whereas matrix in olive oil-based oleogels containing Span only became slightly flexible to release the drug in zero-order fashion on the addition of surfactant cogelator. Conclusion: Nature of oil exerts profound influence on the rheological, thermal and release profile of oleogels containing Span 40 as gelator and/or Tween 80 as surfactant cogelator

HIBISCUS LEAF MUCILAGE AS STABILISER FOR PHARMACEUTICAL DISPERSE SYSTEMS

Objective: Stable pharmaceutical disperse systems are defined as heterogeneous, biphasic systems as suspensions and emulsions, stabilized by third agent or stabilizer. The aim of the present investigation was to extract mucilage from the leaves of Hibiscus rosa-sinesnsis L. and explore its ability to function as stabiliser for adult (10%w/v) and paediatric (2.4%w/v) paracetamol (PCM) suspensions and 2% v/v sunflower oil emulsions. Methods: Isolated mucilage powder was subjected to phytochemical tests to identify the major phytochemical constituents, FTIR spectroscopy to establish compatibility with formulation ingredients, X-ray diffractometry to determine the crystalline nature and viscosity study by Ostwald viscometer and swelling behaviour in water to determine the swelling index. Results: Qualitative phytochemical screening of the mucilage (HM) revealed the presence of non-reducing sugars, gums and mucilage. HM possesses a highly amorphous structure with extremely low overall crystallinity. The mucilage belongs to the class of carbohydrate as it contains–OH groups with intermolecular hydrogen bonding, with 1→4 glycosidic bonds which accounts for its high hydration capacity. Swelling index and relative viscosity of 0.5% w/v mucilage in water was found to be 1050 and 4.84 respectively at 25 °C. Although adult PCM suspensions containing 4% w/v mucilage exhibited poor redispersibility, paediatric suspension containing 1 and 2% w/v mucilage showed gradual settling of particles with good re-dispersibility and flowability. Emulsion activity index (EAI) values of the three emulsions (0.5, 0.75 and 1%w/v HM) were found to be close to 2 g. m-1 ml-1suggesting concentration independent activity of HM as an emulsifier. Emulsion stability index (ESI) values at 72 h showed comparatively less stability with increasing concentration of mucilage probably due to polysaccharide chain overlapping at high concentration leading to less effective surface coverage per unit gum concentration. Conclusion: Therefore, hibiscus leaf mucilage has the capacity to stabilize a suspension or emulsion based on its capacity to adsorb onto solid or liquid interfaces

THERAPEUTIC POTENTIAL OF PLANT-DERIVED OLIGOSTILBENES AND STILBENE GLYCOSIDES

Stilbenoids constitute a major class of plant-derived secondary metabolites occurring in abundance across several families and are well-known for their nutritional and health-promoting benefits. Several investigations have established their therapeutic potential in the management of different types of cancer, neuroinflammation, arthritis, disorders in lipid metabolism, microbial infection etc. Studies on resveratrol monomer, oxyresveratrol, their synthetic analogs, piceatannol, pterostilbene can be found in the literature. But a collective and comprehensive review on chemistry, pharmacological effects, structure-activity relationship and pharmacokinetics of plant-derived oligostilbenes and stilbene glycosides is missing. These phytochemicals are generally characterised by poor oral bioavailability due to extensive first-pass metabolism and conjugation. The present chapter aims to fill up these lacunae and also focuses on further studies that can be performed in the future to translate these immensely potential secondary metabolites into human clinical setting from cell culture and animal studies at the preclinical level for effective therapeutic intervention of various pathological conditions

COMPARATIVE STUDY OF SPAN 40 AND SPAN 60 BASED SOY-GELS FOR TOPICAL DRUG DELIVERY

Objective: Hydrogels or emulgels are recommended for topical application to elicit a local effect. However, they suffer from stability problems. The present study deals with the formulation and comparison of thermally stable soybean oil-based novel topical organogels (soy-gels) using two different gelators (Span 40 and Span 60) for controlled drug delivery. Methods: Soy-gels (8 batches) were developed with Span 40 and Span 60 by solid fiber mechanism and characterized for viscosity, gelation kinetics behavior, gel-sol transition parameters, drug content, in vitro drug release pattern, and changes occurring during accelerated thermal stability studies. Results: Fourier transformed infrared spectroscopic confirmed the compatibility among the organogel components and paracetamol. The formulations exhibited skin and hemocompatibility. The viscosity of Span 60 based soy-gels was found to be approximately 10 times higher than those of Span 40 based formulations. In comparison to Span 40, Span 60 induced faster gelation (3–6 min) of soybean oil at lower concentration (16% w/v) forming less flexible but thermally more stable soy-gels demonstrating higher Tg values. Higher flexibility and lower viscosity accounted for improved drug diffusion (both Fickian and non-Fickian) from Span 40 gels of varying concentrations in pH 5.8. However, zero-order drug release was observed in organogel with 18% w/v Span 40 only and all Span 60-based formulations except the one with 22% w/v Span 60. Non-Fickian drug diffusion occurred from Span 60 based soy-gels. A gradual increase in gelation time was observed until five cycles of freeze-thaw. Conclusion: Therefore, the choice of organogelator governs the rheological, thermal, and drug diffusion properties of soy-gels intended for topical application