Castor Oil

Fortes, Amanda C., et al. Journal of Thermal Analysis & Calorimetry 139.3 (2020): 1949.

Castor oil is an environmentally friendly alternative to hydrocarbon-based feedstocks for polymer synthesis, owing to its high content (approximately 90%) of ricinoleic acid, a bifunctional fatty acid with secondary hydroxyl functionality. Polyurethanes have versatile technological applications in pharmaceutical technology, including use as drug release matrices. This study aimed to obtain and characterize castor oil-based polyurethane (coPU) systems containing domperidone and verapamil hydrochloride as model drugs, evaluating drug-polymer interactions and their influence on drug release.
Experimental Protocol: Castor oil-based polyurethane was prepared by mixing two parts of polyol (component A, containing unreacted castor oil) and one part of prepolymer (component B, containing free NCO groups). Drugs were incorporated using the solvent evaporation method, with 10% drug loading. The drug-loaded systems were characterized by differential scanning calorimetry (DSC), thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM). Drug content was determined by HPLC. Dissolution studies were performed to evaluate drug release profiles, and elemental analysis was conducted on the polymer matrix.
Performance Evaluation: Verapamil hydrochloride was successfully incorporated into the coPU matrix, interacting through hydrogen bonds, and this system demonstrated potential as a candidate for sustained drug release. In contrast, domperidone precipitated during solvent evaporation, resulting in a drug suspension within the polymer matrix. However, approximately 20% of domperidone interacted chemically with the polymer through the reaction of the active hydrogen of domperidone imidazole groups with the terminal isocyanate of the prepolymer. The drug release profile was governed by the drug-polymer physicochemical interaction, which depended on the drug and polymer functional groups that were stereochemically available.

Sandford, Emma C., et al. Clinical and Experimental Optometry 104.3 (2021): 315-322.

Blepharitis, meibomian gland dysfunction, and dry eye disease share a multifactorial pathogenesis that poses challenges to therapeutic management. Current treatments are mostly palliative, with success limited by perceived inefficacy and poor patient compliance. Castor oil, a natural derivative of the Ricinus communis plant, possesses antimicrobial, anti-inflammatory, antioxidant, and wound-healing properties. Its main constituent, ricinoleic acid, has a bipolar molecular structure that may supplement deficient tear lipids and reduce aqueous tear evaporation.
Experimental Protocol: This review synthesized the literature on castor oil's biochemical and medicinal properties relevant to ocular surface disease. Castor oil composition (87-90% ricinoleic acid, with smaller amounts of oleic, linoleic, and palmitic acids) and the bipolar structure of ricinoleic acid were examined. Studies evaluating topical castor oil application to the ocular surface were reviewed, including assessments of residence time, tear lipid layer thickness, tear film stability, ocular surface staining, and symptom improvement. Castor oil's antimicrobial, anti-demodectic, anti-inflammatory, and antioxidant mechanisms were also addressed.
Performance Evaluation: Studies revealed that topical castor oil has a prolonged residence time on the ocular surface, facilitating increased tear lipid layer thickness, improved tear film stability, and reduced ocular surface staining and symptoms. Ricinoleic acid's bipolar structure enables it to supplement deficient physiological tear lipids, enhancing lipid spreading and reducing aqueous tear evaporation. Castor oil demonstrated antimicrobial properties against Staphylococcus species and Propionibacterium acnes, implicated in blepharitis pathogenesis. Commercial ophthalmic preparations containing castor oil have proven effective in counteracting tear film lipid insufficiency. The review concluded that castor oil has significant therapeutic potential in managing ocular surface disease, with a good safety and tolerability profile.

Singh, Vinay K., et al. Journal of applied polymer science 130.3 (2013): 1503-1515.

This study investigated the development of castor oil (CO) and sorbitan monopalmitate (SMP) based organogels as matrices for controlled drug delivery. The organogels were designed to serve as semi-solid formulations capable of sustaining drug release for topical antimicrobial applications. Metronidazole (MZ), a model antimicrobial drug, was incorporated into the gel matrix to evaluate its release kinetics and therapeutic efficacy. The gelation mechanism relied on the self-assembly of SMP molecules within the CO solvent phase, forming a three-dimensional network that immobilizes the solvent and entraps the drug.
Experimental Protocol: Organogels were prepared by heating SMP in CO at 60 degrees C under stirring, followed by cooling to room temperature. The critical gelator concentration was determined by varying SMP from 1% to 30% (w/w). Water-containing gels (GW) were also prepared by incorporating distilled water into the hot SMP-CO solution. The gels were characterized using optical microscopy, fluorescence microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), rheological analysis, impedance spectroscopy, pH measurement, hemocompatibility testing, and antimicrobial evaluation against Bacillus subtilis and Escherichia coli. Accelerated stability was assessed through freeze-thaw cycling and long-term storage per ICH guidelines.
Performance Evaluation: FTIR analysis confirmed strong intramolecular and intermolecular hydrogen bonding among gel components. XRD studies indicated an amorphous nature of the gels. Rheological characterization revealed shear-thinning behavior suitable for topical application. The MZ-loaded gels demonstrated significant antimicrobial activity against both gram-positive and gram-negative bacteria, with clear zones of inhibition observed after 24 hours of incubation. The organogels exhibited satisfactory hemocompatibility and stability under both accelerated and long-term storage conditions. These findings suggest that CO-SMP organogels represent a promising platform for controlled topical delivery of antimicrobial agents.