Structure-function relationship among Quillaja saponins serving as excipients for nasal and ocular delivery of insulin

Comprehensive Review on Applications of Surfactants in Vaccine Formulation, Therapeutic and Cosmetic Pharmacy and Prevention of Pulmonary Failure due to COVID-19

Our world is under serious threat of environmental degradation, climate change and in association with this the out breaks of diseases as pandemics. The devastating impact of the very recent COVID-19, The sharp increase in cases of Cancer, Pulmonary failure, Heart health has triggered questions for the sustainable development of pharmaceutical and medical sciences. In the search of inclusive and effective strategies to meet today’s demand, improvised methodologies and alternative green chemical, bio-based precursors are being introduced by scientists around the globe. In this extensive review we have presented the potentiality and Realtime applications of both synthetic and bio-based surfactants in bio-medical and pharmaceutical fields. For their excellent unique amphoteric nature and ability to solubilise in both organic and inorganic drugs, surfactants are one of the most potential candidates for bio-medicinal fields such as dermatology, drug delivery, anticancer treatment, surfactant therapy, vaccine formulation, personal hygiene care and many more. The self-assembly property of surfactants is a very powerful function for drug delivery systems that increases the bio-availability of the poorly aqueous soluble pharmaceutical products by influencing their solubility. Over the decades many researchers have reported the antimicrobial, anti-adhesive, antibiofilm, anti-inflammatory, antioxidant activities of surfactants regarding its utility in medicinal purposes. In some reports surfactants are found to have spermicidal and laxative activity too. This comprehensive report is targeted to enlighten the versatile applications of Surfactants in drug delivery, vaccine formulation, Cancer Treatment, Therapeutic and cosmetic Pharmaceutical Sciences and prevention of pulmonary failure due to COVID-19.

Recent progress in polymeric non-invasive insulin delivery

The design of carriers for insulin delivery has recently attracted major research attentions in the biomedical field. In general, the release of drug from polymers is driven via a variety of polymers. Several mechanisms such as matrix release, leaching of drug, swelling, and diffusion are usually adopted for the release of drug through polymers. Insulin is one of the most predominant therapeutic drugs for the treatment of both diabetes mellitus; type-I (insulin-dependent) and type II (insulin-independent). Currently, insulin is administered subcutaneously, which makes the patient feel discomfort, pain, hyperinsulinemia, allergic responses, lipodystrophy surrounding the injection area, and occurrence of miscarried glycemic control. Therefore, significant research interest has been focused on designing and developing new insulin delivery technologies to control blood glucose levels and time, which can enhance the patient compliance simultaneously through alternative routes as non-invasive insulin delivery. The aim of this review is to emphasize various non-invasive insulin delivery mechanisms including oral, transdermal, rectal, vaginal, ocular, and nasal. In addition, this review highlights different smart stimuli-responsive insulin delivery systems including glucose, pH, enzymes, near-infrared, ultrasound, magnetic and electric fields, and the application of various polymers as insulin carriers. Finally, the advantages, limitations, and the effect of each non-invasive route on insulin delivery are discussed in detail.

Natural and Synthetic Saponins as Vaccine Adjuvants

Saponin adjuvants have been extensively studied for their use in veterinary and human vaccines. Among them, QS-21 stands out owing to its unique profile of immunostimulating activity, inducing a balanced Th1/Th2 immunity, which is valuable to a broad scope of applications in combating various microbial pathogens, cancers, and other diseases. It has recently been approved for use in human vaccines as a key component of combination adjuvants, e.g., AS01b in Shingrix^® for herpes zoster. Despite its usefulness in research and clinic, the cellular and molecular mechanisms of QS-21 and other saponin adjuvants are poorly understood. Extensive efforts have been devoted to studies for understanding the mechanisms of QS-21 in different formulations and in different combinations with other adjuvants, and to medicinal chemistry studies for gaining mechanistic insights and development of practical alternatives to QS-21 that can circumvent its inherent drawbacks. In this review, we briefly summarize the current understandings of the mechanism underlying QS-21’s adjuvanticity and the encouraging results from recent structure-activity-relationship (SAR) studies.

Impact of C28 Oligosaccharide on Adjuvant Activity of QS-7 Analogues

We have synthesized a number of Quillaja saponaria Molina (QS) saponin analogues with a different C28 sugar unit, which features either 3,4-diacetyl groups or a 3,4-cyclic carbonate group at the reducing end fucoside to mimic the naturally occurring saponin adjuvant QS-7. Immunological evaluations of these analogues in BALB/c mice indicate that truncating the C28 oligosaccharide of the natural product to the tetrasaccharide (as in 5d (β)) could retain the adjuvant's activity in enhancing IgG1 and IgG2a productions, albeit the activity is lower than that of QS-21. Further truncation or changing stereochemistry of glycosidic linkage between the tetrasaccharide and the triterpenoid quillaic acid (QA) core or within the tetrasaccharide eliminated the saponins' adjuvant activity in terms of IgG production. On the other hand, increasing resemblance to QS-7 increased adjuvant activity and led to saponin 3's similar IgG1 and IgG2a activities to QS-21's, indicating that the unique adjuvant activities of QS saponins are determined by their specific structures.

Vaccine Adjuvants Derivatized from Momordica Saponins I and II

We have derivatized Momordica saponins (MS) I and II through their coupling at C3 glucuronic acid site with dodecylamine. The derivatives show significantly different immunostimulant activity profiles from their respective natural parent saponins. In particular, adjuvant VSA-1 (5), the derivative of MS I, potentiates a significantly higher IgG2a responose than the corresponding natural product. Its IgG1 and IgG2a production is similar to that of GPI-0100, indicating a potential mixed and antigen-specific Th1/Th2 immune response, which is different from the Th2 immunity induced by the natural saponin MS I. In addition, toxicity evaluations show that adjuvant VSA-1 (5) is much less toxic than the widely used natural saponin mixture Quil A. These results prove that derivatizing Momordica saponins can be a viable way for easy access to structurally defined saponin immunostimulants with favorable adjvuant activity and low toxicity.

Stability of saponin biopesticides: hydrolysis in aqueous solutions and lake waters

Saponins form a group of plant-produced glycosides with potential as biopesticide ingredients. The environmental fate of saponins has never been fully investigated. In the present study, we use QS-18, a specific saponin from Quillaja saponaria as an example, to quantify hydrolysis under different conditions of pH, temperature and water chemical composition. Saponin hydrolysis in buffer solutions was base-catalyzed and followed first-order kinetics. Thus, hydrolysis was slow at pH 5.1 with a half-life of 330 ± 220 d (26 °C), which increases to 0.06 ± 0.01 d at pH 10.0. Hydrolysis rates were highly sensitive to temperature with an activation energy of 56.9 ± 14.2 kJ mol-1 at pH 7.2. In strong contrast, hydrolysis in lake waters (pH 6.4-8.2) produced different patterns with a fast initial dissipation of 25 to 60% of the added saponin within the first five hours, followed by an extremely slow reaction with 25 to 75% unreacted saponin left after reaction times longer than 120 h. The fast dissipation followed by slow hydrolysis in lake water was hypothesized to be attributed to sorption and/or flocculation of saponins by inorganic nanoparticles and/or solutes in the lake water followed by inactivation of hydrolysis due to the sorption/flocculation. The present study demonstrates that saponins may hydrolyze slowly under acidic and cold conditions. In addition, it demonstrates that dissipation kinetics in natural waters may deviate substantially from the kinetics predicted based on laboratory experiments with "clean" buffered solutions. This emphasizes the need for a deeper understanding of the processes affecting the dissipation kinetics of potential toxins under natural conditions, as fate models based on laboratory derived kinetic data may be seriously flawed.

Where does the toxicity come from in saponin extract?

Saponin-rich plant extracts contain bioactive natural compounds and have many applications, e.g. as biopesticides and biosurfactants. The composition of saponin-rich plant extracts is very diverse, making environmental monitoring difficult. In this study various ecotoxicity data as well as exposure data have been collected to explore which compounds in the plant extract are relevant as plant protection agents and furthermore to clarify which compounds may cause undesired side-effects due to their toxicity. Hence, we quantified the toxicity of different fractions (saponins/non-saponins) in the plant extracts on the aquatic crustacean Daphnia magna and zebrafish (Danio rerio) embryos. In addition, we tested the toxicity changes during saponin degradation as well. The results confirm that saponins are responsible for the majority of toxicity (85.1-93.6%) of Quillaja saponaria extract. We, therefore, suggest saponins to be the main target of saponin-rich plant extracts, for instance in the saponin-based biopesticide regulation. Furthermore, we suggest that an abundant saponin fraction, QS-18 from Q. saponaria, can be a key monitoring target to represent the environmental concentration of the saponins, as it contributes with 26% and 61% of the joint toxicity to D. magna and D. rerio, respectively out of the total saponins. The degradation products of saponins are 3-7 times less toxic than the parent compound; therefore the focus should be mainly on the parent compounds.

Synthesis and Evaluation of QS-21-Based Immunoadjuvants with a Terminal-Functionalized Side Chain Incorporated in the West Wing Trisaccharide

Three QS-21-based vaccine adjuvant candidates with a terminal-functionalized side chain incorporated in the west wing trisaccharide have been synthesized. The terminal polar functional group serves to increase the solubility of these analogues in water. Two of the synthetic analogues have been shown to have adjuvant activity comparable to that of GPI-0100. The stand-alone adjuvant activity of the new synthetic analogues again confirmed that it is a feasible way to develop new saponin-based vaccine adjuvants through derivatizing at the west wing branched trisaccharide domain. Inclusion of an additional polar functional group such as a carboxyl group (as in 3x) or a monosaccharide (as in 4x and 5x) is sufficient to increase the water solubility of the corresponding synthetic analogues to a level comparable to that of GPI-0100 and suitable for immunological studies and clinical application. The structure of the incorporated side chain has a significant impact on the adjuvant activity in terms of the magnitude and nature of the host's responses.

Absorption-Enhancing Effects of Bile Salts

Bile salts are ionic amphiphilic compounds with a steroid skeleton. Among the most important physiological properties of bile salts are lipid transport by solubilization and transport of some drugs through hydrophobic barriers. Bile salts have been extensively studied to enhance transepithelial permeability for different marker molecules and drugs. They readily agglomerate at concentrations above their critical micelle concentration (CMC). The mechanism of absorption enhancement by bile salts appears to be complex. The aim of the present article was to review bile salt structure and their application as absorption enhancers and the probable mechanism for increasing permeation based on previous studies.

The amphiphilic nature of saponins and their effects on artificial and biological membranes and potential consequences for red blood and cancer cells

Saponins, amphiphiles of natural origin with numerous biological activities, are widely used in the cosmetic and pharmaceutical industry. Some saponins exhibit relatively selective cytotoxic effects on cancer cells but the tendency of saponins to induce hemolysis limits their anticancer potential. This review focused on the effects of saponin activity on membranes and consequent implications for red blood and cancer cells. This activity seems to be strongly related to the amphiphilic character of saponins that gives them the ability to self-aggregate and interact with membrane components such as cholesterol and phospholipids. Membrane interactions of saponins with artificial membrane models, red blood and cancer cells are reviewed with respect to their molecular structures. The review considered the mechanisms of these membrane interactions and their consequences including the modulation of membrane dynamics, interaction with membrane rafts, and membrane lysis. We summarized current knowledge concerning the mechanisms involved in the interactions of saponins with membrane lipids and examined the structure activity relationship of saponins regarding hemolysis and cancer cell death. A critical analysis of these findings speculates on their potential to further develop new anticancer compounds.

Synthesis of QS-21-based immunoadjuvants

Three structurally defined QS-21-based immune adjuvant candidates (2a-2c) have been synthesized. Application of the two-stage activation glycosylation approach utilizing allyl glycoside building blocks improved the synthetic accessibility of the new adjuvants. The efficient synthesis and establishment of the stand-alone adjuvanticity of the examined synthetic adjuvant (2b) open the door to the pursuit of a new series of structurally defined QS-saponin-based synthetic adjuvants.

Dietary kakrol (Momordica dioica Roxb.) flesh inhibits triacylglycerol absorption and lowers the risk for development of fatty liver in rats

Kakrol ( Momordica dioica Roxb.) is a cucurbitaceous vegetable native to India and Bangladesh. Bitter gourd ( Momordica charantia Linn.), a species related to kakrol, has been shown to have pharmacological properties including antidiabetic and antisteatotic effects. In this study, we investigated the effect of dietary kakrol on lipid metabolism in rats. Sprague-Dawley rats were fed AIN-76 formula diets containing 3% freeze-dried powders of whole kakrol or bitter gourd for two weeks. Results showed significantly lowered liver cholesterol and triacylglycerol levels in rats fed on both diets. Fecal lipid excretion increased in rats fed the kakrol diet, and lymphatic transport of triacylglycerol and phospholipids decreased in rats fed the kakrol diet after permanent lymph cannulation. Furthermore, n-butanol extract from kakrol caused a significant concentration-dependent decrease in the pancreatic lipase activity in vitro. These results indicate that the mechanisms of action on lipid metabolism in kakrol and bitter gourd are different and that dietary kakrol reduces liver lipids by inhibiting lipid absorption.

Prevention of rotavirus infections in vitro with aqueous extracts of Quillaja Saponaria Molina

BACKGROUND

Rotavirus is the leading cause of severe diarrhea disease in newborns and young children worldwide, estimated to be responsible for over 300,000 childhood deaths every year, mostly in developing countries. Rotavirus-related deaths represent approximately 5% of all deaths in children younger than 5 years of age worldwide. Saponins are readily soluble in water and are approved by the US FDA for inclusion in beverages intended for human consumption. The addition of saponins to existing water supplies offers a new form of intervention into the cycle of rotavirus infection. We believe that saponins will 'coat' the epithelium of the host's small intestine and prevent attachment of rotavirus.

DISCUSSION

This experiment provides in vitro data for the possibility of including saponin in drinking water to prevent infections of rotavirus. We demonstrate that microgram amounts of extract, while exhibiting no cell cytotoxicity or direct virucidal activity, prevent rotavirus from infecting its host cells. In addition, the presence of residual amounts of extract continue to block viral infection and render cells resistant to infection for at least 16 h after the removal of the extract from the cell culture media.

CONCLUSION

We demonstrate that two Quillaja extracts possess strong antiviral activity at concentrations more than 1000-fold lower than concentrations exhibiting cell cytotoxicity. Extract concentrations as high as 1000 μg/ml are not cytotoxic, but concentrations as low as 1.0 μg/ml are able to block rotavirus and reovirus attachment and infection.

Hemolytic and antimicrobial activities differ among saponin-rich extracts from guar, quillaja, yucca, and soybean

Hemolytic and antibacterial activities of eight serial concentrations ranged from 5-666 microg/mL of saponin-rich extracts from guar meal (GM), quillaja, yucca, and soybean were tested in 96-well plates and read by enzyme-linked immunosorbent assay plate-well as 650 nm. Hemolytic assay used a 1% suspension of chicken red blood cells with water and phosphate buffered saline as positive and negative controls, respectively. Antibacterial activity against Staphylococcus aureus, Salmonella typhimurium, and Escherichia coli were evaluated using ampicillin and bacteria without saponin-rich extract as positive and negative controls, respectively. The 100% MeOH GM and commercial quillaja saponin-rich extracts were significantly the highest in both hemolytic and antibacterial activities against all bacteria at the same concentration tested. Soybean saponin-rich extract had no antibacterial activity against any of the bacteria at the concentrations tested while yucca saponin-rich extract had no antibacterial activity against the gram-negative bacteria at the concentrations tested. GM and quillaja saponin-rich extracts were hemolytic, while yucca and soybean saponin-rich extracts were not hemolytic at the concentrations tested. No saponin-rich extract source had antibacterial activity against S. typhimurium or E. coli at the concentrations tested. Both GM and quillaja saponin-rich extracts exhibited antibacterial activity against S. aureus. Saponin-rich extracts from different plant sources have different hemolytic and antibacterial activities.

Adjuvant activities of saponins from traditional Chinese medicinal herbs

New generation vaccines such as recombinant, antigen purified and DNA vaccines are poorly immunogenic due to the lack of an innate immune stimulus. Therefore, search of new adjuvants for these vaccines has become a topic of interesting. In new adjuvant development, saponins are outstanding candidates. Recently, increased attention has been received on plant-derived saponins in search of new adjuvant candidates from traditional Chinese medicinal herbs such as Panax ginseng, Astragalus species, Panax notoginseng,Cochinchina momordica, Glycyrrhiza uralensis and Achyranthes bidentata. Many of the saponins have been found to have adjuvant effects on purified protein antigens. The chemical structures of the saponins are related to their adjuvant activities, and influence the nature of the immune responses. Saponin adjuvants have been reported to stimulate secretion of a broad range of cytokines, suggesting that saponins may act by triggering innate immunity. As these plant-originated adjuvants may promote different branches of the immune system, they have the potential to be used in design of new vaccines so as to induce a desired immune response.

Advances in saponin-based adjuvants

Saponins are natural glycosides of steroid or triterpene which exhibited many different biological and pharmacological activities. Notably, saponins can also activate the mammalian immune system, which have led to significant interest in their potential as vaccine adjuvants. The most widely used saponin-based adjuvants are Quil A and its derivatives QS-21, isolated from the bark of Quillaja saponaria Molina, which have been evaluated in numerous clinical trials. Their unique capacity to stimulate both the Th1 immune response and the production of cytotoxic T-lymphocytes (CTLs) against exogenous antigens makes them ideal for use in subunit vaccines and vaccines directed against intracellular pathogens as well as for therapeutic cancer vaccines. However, Quillaja saponins have serious drawbacks such as high toxicity, undesirable haemolytic effect and instability in aqueous phase, which limits their use as adjuvant in vaccination. It has driven much research for saponin-based adjuvant from other kinds of natural products. This review will summarize the current advances concerning adjuvant effects of different kinds of saponins. The structure-activity relationship of saponin adjuvants will also be discussed in the light of recent findings. It is hoped that the information collated here will provide the reader with information regarding the adjuvant potential applications of saponins and stimulate further research into these compounds.

Assessment of the monoterpene, glycidic and triterpene-moieties’ contributions to the adjuvant function of the CP05 saponin of Calliandra pulcherrima Benth during vaccination against experimental visceral leishmaniasis

The CP05 saponin from Calliandra pulcherrima Benth, shows remarkable similarities to the QS21 saponin of Quillaja saponaria Molina. Both shared a monoterpene hydrophobic moiety, a glycidic chain attached to the triterpene C28, and three sugars attached to C3. Different from QS21, the CP05 does not show the aldehyde group in triterpene C4 involved in TH1 response. Balb/c mice were immunized either intact saponin (CP05), the monoterpene-deprived (BS), the C28 carbohydrate-deprived (HS) or the sapogenin fraction, in formulation with the FML antigen of Leishmania donovani and challenged with 2 x 10(8) amastigotes of L. chagasi. While the CP05 induced 90% survival and 92.1% parasite reduction, a 100% survival and 94.1% protection were detected after the BS-vaccine treatment, indicating that the monoterpene acylated moiety, absent in the BS vaccine, is not necessary for the induction of a protective global TH1 response. Only the DTH response of BS vaccines was mildly lower than that of CP05 vaccinees. Maximal anti-FML antibody, CD4(+) and CD8(+) Leishmania specific lymphocytes, IFN-gamma splenocyte secretion, reduction in parasite load and survival was also detected for the BS vaccine. The HSFML vaccine showed diminished responses in all tested variables, except for IFN-gamma secretion, indicating that the integrity of the carbohydrate moiety attached to C28 is mandatory for the these functions. No protection was induced by the sapogenin-FML indicating that the CP05 triterpene which lacks the C4 aldehyde group, is not a immunostimulating compound. No contribution to protection was detected in the CP05 saponin treated control group supporting the specificity of the FML antigenic preparation.

Micellar nanocarriers: pharmaceutical perspectives

Micelles, self-assembling nanosized colloidal particles with a hydrophobic core and hydrophilic shell are currently successfully used as pharmaceutical carriers for water-insoluble drugs and demonstrate a series of attractive properties as drug carriers. Among the micelle-forming compounds, amphiphilic copolymers, i.e., polymers consisting of hydrophobic block and hydrophilic block, are gaining an increasing attention. Polymeric micelles possess high stability both in vitro and in vivo and good biocompatibility, and can solubilize a broad variety of poorly soluble pharmaceuticals many of these drug-loaded micelles are currently at different stages of preclinical and clinical trials. Among polymeric micelles, a special group is formed by lipid-core micelles, i.e., micelles formed by conjugates of soluble copolymers with lipids (such as polyethylene glycol-phosphatidyl ethanolamine conjugate, PEG-PE). Polymeric micelles, including lipid-core micelles, carrying various reporter (contrast) groups may become the imaging agents of choice in different imaging modalities. All these micelles can also be used as targeted drug delivery systems. The targeting can be achieved via the enhanced permeability and retention (EPR) effect (into the areas with the compromised vasculature), by making micelles of stimuli-responsive amphiphilic block-copolymers, or by attaching specific targeting ligand molecules to the micelle surface. Immunomicelles prepared by coupling monoclonal antibody molecules to p-nitrophenylcarbonyl groups on the water-exposed termini of the micelle corona-forming blocks demonstrate high binding specificity and targetability. This review will discuss some recent trends in using micelles as pharmaceutical carriers.

Immunological adjuvant activities of saponin extracts from the pods of Acacia concinna

Pods of Acacia concinna (Leguminosae) contain several saponins. In this study, four saponin fractions which were acetone fraction (AAC), aqueous fraction (WAC), hydromethanolic fraction (HAC) and methanolic fraction (MAC) were generated and their haemolytic activities and surface activities were determined in comparison with quillaja saponin (QS). There were no significant differences between the haemolytic activities of MAC and QS. However, the surface tensions of MAC was significantly lower than QS (p < 0.001). Furthermore, the immunomodulatory effect and the adjuvant potential of MAC on the cellular and humoral immune response of BALB/c mice against ovalbumin were investigated. The splenocyte proliferations induced by MAC were significantly higher than QS at the concentrations of 200, 400, 800 and 1000 microg/ml (p < 0.05). BALB/c mice were immunized subcutaneously either with OVA 20 microg alone or with OVA 20 microg combining with QS (10 microg) or MAC (10 and 40 microg). Ten days after the second immunization, concanavalin A (Con A)-, pokeweed mitogen (PWM)-, and OVA-stimulated splenocyte proliferation and OVA-specific antibodies in serum were measured. The results suggested that MAC (40 microg) could activate T and B cells. In addition, OVA-specific IgG, IgG1 IgG2a and IgG2b antibody levels in serum were significantly enhanced by MAC (40 microg) as compared with OVA control group (p < 0.001). This finding suggested that MAC might be effect on Th1 and Th2 helper T cells. In conclusion, the results indicated that MAC at a dose of 40 microg could be used as vaccine adjuvant to increase immune responses.

Acylated and deacylated saponins of Quillaja saponaria mixture as adjuvants for the FML-vaccine against visceral leishmaniasis

The adjuvant of the FML-vaccine against murine and canine visceral leishmaniasis, the Riedel de Haen saponin mixture, was fractionated by ion exchange chromatography on DEAE-cellulose to afford one TLC homogeneous Quillaja saponaria Molina QS21 saponin fraction (18.0%), a mixture of two deacylsaponins (19.4%), sucrose (39.9%), sucrose and glucose (19.7%), rutin (0.8%) and quercetin (2.2%), that were identified by comparison of 1H and 13C NMR spectroscopy. The QS21 shows the typical aldehyde group in C-23 (65% equatorial) and a normonoterpene moiety acylated in C-28. The deacylsaponins show the aldehyde group but do not have the normonoterpene moiety. Balb/c mice were vaccinated with 150 microg of FML antigen of Leishmania donovani and 100 microg of each obtained fraction and further challenged by infection with 10(8) amastigotes of Leishmania chagasi. The safety analysis and the effect on humoral and cellular immune responses and in clinical signs showed that the QS21 saponin and the deacylsaponins are the most active adjuvant compounds of the Riedel the Haen saponin mixture. Both induced the highest and non-significantly different increases in DTH, CD4+ T lymphocytes in spleen, IFN-gamma in vitro, body weight gain and the most pronounced reduction of parasite burden in liver (95% for QS21 and 86% for deacylsaponins; p>0.05). While the QS21 showed mild toxicity, significant adjuvant effect on the anti-FML humoral response before and after infection, and decrease in liver relative weight, the deacylsaponins showed no toxicity, less haemolysis and antibody and DTH responses increased mainly after infection, still inducing a stronger Leishmania-specific in vitro splenocyte proliferation. Our results confirm in the Riedel de Haen saponin extract the presence of deacylsaponins normonoterpene-deprivated which are non-toxic and capable of inducing a specific and strong immunoprotective response in vaccination against murine visceral leishmaniasis.

Micellar aggregation and membrane partitioning of bile salts, fatty acids, sodium dodecyl sulfate, and sugar-conjugated fatty acids: correlation with hemolytic potency and implications for drug delivery

The co-administration of a drug with a penetration enhancer (PE) is one method by which the membrane permeability of a drug can be improved. To facilitate PE design, it is important that the molecular basis of PE toxicity and efficacy be examined, so we investigated the membrane affinity and micellar aggregation of a series of synthetic liposaccharide PEs and correlated these properties with hemolytic potency. The influence of liposaccharide alkyl chain length (nc) on the system was studied, and comparisons were made with conventional PEs such as bile salts, fatty acids, and surfactants. The liposaccharides were each synthesized in eight steps in good overall yield. Their critical micelle concentrations (CMCs) in phosphate-buffered saline ranged from 0.207 to 20.2 mM, and it was found that increasing nc by 2 afforded a 1 order of magnitude decrease in the CMC. Immobilized artificial membrane (IAM) chromatography was used to determine each PE's affinity for biological membranes, and an increase in nc caused a significant increase in the extent of membrane binding. A study of hemolytic activity revealed that liposaccharides with an nc of < or = 12 are the most likely to be biocompatible. The CMC values for all PEs showed a negative correlation with hemolytic potency; however, it was PE monomers, not micelles, that were responsible for the onset of hemolysis. The affinity of all enhancers for the IAM displayed a positive correlation with hemolytic potency, and therefore, IAM chromatography can be used to predict PE hemolytic activity. It was concluded that the biocompatibility of liposaccharides can be modulated by minor alterations in nc.

Enhancement of ovalbumin-specific IgA responses via oral boosting with antigen co-administered with an aqueous Solanum torvum extract

An experiment was conducted with the objective to enhance mucosal immunity against ovalbumin (OVA) by co-administration of OVA with an aqueous extract from the fruit of Solanum torvum (STE). Five groups of female ICR mice aged approximately 8 weeks at the commencement of the experiment were caged in groups of eight and received various treatments. The treatments included OVA alone, OVA with cholera toxin (CT), and OVA with various doses of STE. Mice were primed intraperitoneally with 500 microg of OVA alone or co-administered with 0.1 microg CT, or with 1 microg STE. All mice were boosted orally via gastric intubation 14 days after priming with 10 mg OVA alone, or co-administered with 10 microg CT or with 10 mg, 1 mg or 0.1 mg STE. One week later all mice were killed and organs obtained for analysis of the immune response. Intestinal, faecal and pulmonary OVA-specific sIgA concentration was significantly increased (p<0.05) in mice that received booster combinations of OVA/CT and OVA with all extract doses (p<0.05). Specific serum IgG titres did not differ significantly between groups. It is concluded that STE can significantly enhance secretory immunity in the intestine to OVA with mucosal homing to the lungs. The adjuvant effect of STE is comparable to that of CT.

The biological action of saponins in animal systems: a review

Saponins are steroid or triterpenoid glycosides, common in a large number of plants and plant products that are important in human and animal nutrition. Several biological effects have been ascribed to saponins. Extensive research has been carried out into the membrane-permeabilising, immunostimulant, hypocholesterolaemic and anticarcinogenic properties of saponins and they have also been found to significantly affect growth, feed intake and reproduction in animals. These structurally diverse compounds have also been observed to kill protozoans and molluscs, to be antioxidants, to impair the digestion of protein and the uptake of vitamins and minerals in the gut, to cause hypoglycaemia, and to act as antifungal and antiviral agents. These compounds can thus affect animals in a host of different ways both positive and negative.

Penetration enhancers and ocular bioadhesives: two new avenues for ophthalmic drug delivery

This review is focused on the two avenues of development that promise a major impact on future ocular drug therapeutics: bioadhesives, including hydrogels and other agents like carbopols, polyacrylic acids, chitosan, etc., and penetration enhancers, including different surfactants, calcium chelators, etc. The capacity of some polymers to adhere to the mucin coat covering the conjunctiva and the corneal surface of the eye forms the basis for ocular mucoadhesion. These systems markedly prolong the residence time of a drug in the conjunctival sac, since clearence is now controlled by the much slower rate of mucus turnover rather than the tear turnover rate. But improving the corneal drug retention alone is inadequate in bringing about a significant improvement of drug bioavailability. Another approach consists of transiently increasing the pentration characteristics of the cornea with appropriate substances, known as penetration enhancers or absorption promoters. The main aim of this article is to give an insight into the potential application of mucoadhesives and corneal penetration enhancers for the conception of innovative opthalmic delivery appraoches, to decrease the systemic side effects, and create a more focused effect, which may be achieved with lower doses of the drug. Ophthalmic formulations based on these mucoadhesives and penetration enhancers are simple to manufacture and exhibit an excellent tolerance when administered into the cornea. The use of the former considerably prolongs the corneal contact time and the use of the latter increases the rate and amount of drug transport. The various corneal epithelial barriers along with the major routes of transport of drugs are discussed. The article includes a list of the various substances in use or under investigation for the aforementioned properties, along with their mechanisms of action. A fair appraisal of the subject with regard to these two therapeutic approaches and any expected ill effects has been made.

Review on the systemic delivery of insulin via the ocular route

Systemic drug absorption from the ocular route is well known. Although there is some absorption from the conjunctival sac, the nasal meatus is the site where the majority of systemic absorption of instilled drug takes place. This article reviews the principles of systemic absorption of insulin applied topically to the eye. The physiological and pharmaceutical considerations for formulation development and the strategy of improving the systemic absorption and bioavailability of insulin are also discussed.

Enhancement of paracellular transport of heparin disaccharide across Caco-2 cell monolayers

The enhancement of paracellular transport of heparin disaccharide using several absorption enhancers across Caco-2 cell monolayers was tested. The cytotoxicity of these enhancers was also examined. The enhancing effects by Quillaja saponin, dipotassium glycyrrhizinate, 18beta-glycyrrhetinic acid, sodium caprate and taurine were determined by changes in transepithelial electrical resistance (TEER) and the amount of heparin disaccharide transported across Caco-2 cell monolayers. Among the absorption enhancers, 18beta-glycyrrhetinic acid and taurine decreased TEER and increased the permeability of heparin disaccharide in a dose-dependent and time-dependent manner with little or negligible cytotoxicity. Our results indicate that these absorption enhancers can widen the tight junction, which is a dominant paracellular absorption route of hydrophilic compounds. It is highly possible that these absorption enhancers can be applied as pharmaceutical excipients to improve the transport of macromolecules and hydrophilic drugs having difficulty in permeability across the intestinal epithelium.

Onjisaponins, from the root of Polygala tenuifolia Willdenow, as effective adjuvants for nasal influenza and diphtheria-pertussis-tetanus vaccines

Active substances from hot water extracts from 267 different Chinese and Japanese medicinal herbs were screened for mucosal adjuvant activity with influenza HA vaccine in mice. The extract from the root of Polygala tenuifolia was found to contain potent mucosal adjuvant activity. The active substances were purified and identified as onjisaponins A, E, F, and G. When each onjisaponin (10 microg) was intranasally (i.n.) inoculated with influenza vaccine (10 microg) in mice, serum hemagglutination-inhibiting (HI) antibody titers increased 3-14 times over control mice administered vaccine alone after 4 weeks. When each onjisaponin (10 microg) was i.n. inoculated with the vaccine (10 microg) followed by i.n. vaccination of the vaccine alone after 3 weeks, serum HI antibody titers increased 27-50 fold over those mice given i.n. vaccinations without onjisaponins. These same conditions also significantly increased nasal anti-influenza virus IgA antibody titers. Two inoculations with onjisaponin F (1 microg) and influenza HA vaccine (1 microg) at 3 weeks intervals, significantly increased serum HI antibody and nasal anti-influenza virus IgA and IgG antibody titers after only 1 week over mice given HA vaccine alone after the secondary vaccination. Intranasal vaccination with onjisaponin F inhibited proliferation of mouse adapted influenza virus A/PR/8/34 in bronchoalveolar lavages of infected mice. Separate intranasal vaccinations with onjisaponins A, E, F, and G (10 microg) each and diphtheria-pertussis-tetanus (DPT) vaccine (10 microg) of mice followed by i.n. vaccination with DPT vaccine alone after 4 weeks showed significant increases in serum IgG and nasal IgA antibody titers after 2 weeks following secondary vaccination over mice vaccinated with DPT vaccine alone. All onjisaponins showed little hemolytic activity at concentrations up to 100 microg/ml. The results of this study suggest that onjisaponins may provide safe and potent adjuvants for intranasal inoculation of influenza HA and DPT vaccines.

Inhalation therapy: new delivery systems

The objective of this article is to provide an overview of recent advances in inhalation drug delivery. Problems, advantages, limitations, and developments encountered by different inhalation devices and the agents used in these for the purpose of pulmonary delivery are discussed. A critical appraisal is presented and finally the future directions especially in research of the inhaled therapeutics and aerosols are described.

Cholesterol solubilization in aqueous micellar solutions of quillaja saponin, bile salts, or nonionic surfactants

Quillaja saponin in aqueous solution enhanced cholesterol solubility by as much as a factor of 10(3) at room temperature. Increased temperature and [NaCl] increased cholesterol solubility, whereas solubility was greatest at an aqueous pH of 4.6 at 298 K. Although various saponin sources were observed to differ in their abilities to solubilize cholesterol, trends in their solubilization properties with changing aqueous phase parameters were consistent. Surfactant molecules containing fused-ring structures as their hydrophobic portion, such as sodium cholate, sodium deoxycholate, and quillaja saponin, solubilized cholesterol significantly better than the linear hydrocarbon chain surfactants Tween 20 and Triton X-100. Mixtures of surfactants studied were found to exhibit synergistic effects: they formed micelles at lower concentrations than did those formed by the individual surfactants themselves, and they had a better ability to solubilize cholesterol. The knowledge obtained from these studies improves our understanding of cholesterol association with saponin and other types of surfactants and enhances the potential for using saponins for the solubilization and extraction of hydrophobic solutes in various pharmacological and industrial applications.

Microparticle resins as a potential nasal drug delivery system for insulin

The application of various resins for the nasal delivery of insulin was examined in rabbits. Intranasal administration of human insulin (28 U, 1 mg) mixed with fractionated sodium polystyrene sulfonate powder (an anionic resin with a particle size of 20-45 microns) caused a rapid increase of the plasma insulin level 413.0 +/- 71.7 microU/ml (mean +/- S.D.) after 15 min, while intranasal administration of insulin alone caused little increase. The blood glucose level decreased from 118.8 +/- 18.5 mg/dl to 65.8 +/- 13.8 mg/dl at 45 min after administration. These results were superior to those obtained with the unfractionated resin. Styrene-divinylbenzene copolymer (a nonionic resin; 20-45 microns fraction) showed similar enhancement of nasal insulin absorption. In contrast, polyacrylester (a nonionic resin; 20-45 microns fraction) and cholestyramine (a cationic resin) did not promote insulin absorption. These results suggest that some resins may be useful for nasal delivery of insulin.

A semisynthetic Quillaja saponin as a drug delivery agent for aminoglycoside antibiotics

PURPOSE

The purpose of this study was to investigate the utility of a purified, semisynthetic saponin, DS-1, prepared by deacylation of a naturally occurring saponin from the bark of the Quillaja saponaria Molina tree, as a permeation enhancer for mucosal delivery of the aminoglycosides, gentamicin and tobramycin.

METHODS

Gentamicin or tobramycin formulations, with and without DS-1, were administered to rats nasally, ocularly, and rectally. Serum aminoglycoside levels following mucosal application were compared with those administered intramuscularly. Gentamicin formulations, with and without DS-1, were administered intranasally to mice 60 minutes after a lethal bacterial challenge. To ascertain nasal irritation potential, DS-1 nosedrops were administered to rats twice daily for 7 days in the right nostril only. Comparison of the left (internal control) and right nostril was made with a control group that received only buffer.

RESULTS

Significant transport across mucous membranes was only observed in formulations containing DS-1. This effect on drug delivery was transient. Administration of an intranasal gentamicin/DS-1 formulation reversed the lethal bacterial challenge in mice, demonstrating that biological activity was retained after absorption. Nasal irritation was not observed in groups receiving DS-1 nosedrops, which were identical to control groups.

CONCLUSIONS

DS-1 has potential as a transmucosal delivery agent for the aminoglycoside antibiotics.