[Toxicological studies on sophorolipid derivatives. (I). Acute toxicity, eye irritation, primary skin irritation, skin sensitization, phototoxicity, photosensitization, mutagenicity of polyoxypropylene (12) [(2'-0-beta-D-glucopyranosyl-beta-D-glucopyranosyl)oxy-] fatty acid ester-]

Microbial sophorolipids inhibit colorectal tumour cell growth in vitro and restore haematocrit in Apcmin+/- mice

Abstract

Sophorolipids are glycolipid biosurfactants consisting of a carbohydrate sophorose head with a fatty acid tail and exist in either an acidic or lactonic form. Sophorolipids are gaining interest as potential cancer chemotherapeutics due to their inhibitory effects on a range of tumour cell lines. Currently, most anti-cancer studies reporting the effects of sophorolipids have focused on lactonic preparations with the effects of acidic sophorolipids yet to be elucidated. We produced a 94% pure acidic sophorolipid preparation which proved to be non-toxic to normal human colonic and lung cells. In contrast, we observed a dose-dependent reduction in viability of colorectal cancer lines treated with the same preparation. Acidic sophorolipids induced apoptosis and necrosis, reduced migration, and inhibited colony formation in all cancer cell lines tested. Furthermore, oral administration of 50 mg kg⁻¹ acidic sophorolipids over 70 days to Apc^min+/− mice was well tolerated and resulted in an increased haematocrit, as well as reducing splenic size and red pulp area. Oral feeding did not affect tumour numbers or sizes in this model. This is the first study to show that acidic sophorolipids dose-dependently and specifically reduces colon cancer cell viability in addition to reducing tumour-associated bleeding in the Apc^min+/− mouse model.

Key points

• Acidic sophorolipids are produced by yeast species such as Starmerella bombicola.

• Acidic sophorolipids selectively killed colorectal cells with no effect on healthy gut epithelia.

• Acidic sophorolipids reduced tumour-associated gut bleed in a colorectal mouse model.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-022-12115-6.

Biosurfactants as a Novel Additive in Pharmaceutical Formulations: Current Trends and Future Implications

BACKGROUND

Surfactants are an important category of additives that are used widely in most of the formulations as solubilizers, stabilizers, and emulsifiers. Current drug delivery systems comprise of numerous synthetic surfactants (such as Cremophor EL, polysorbate 80, Transcutol-P), which are associated with several side effects though used in many formulations. Therefore, to attenuate the problems associated with conventional surfactants, a new generation of surface-active agents is obtained from the metabolites of fungi, yeast, and bacteria, which are termed as biosurfactants.

OBJECTIVES

In this article, we critically analyze the different types of biosurfactants, their origin along with their chemical and physical properties, advantages, drawbacks, regulatory status, and detailed pharmaceutical applications.

METHODS

243 papers were reviewed and included in this review.

RESULTS

Briefly, Biosurfactants are classified as glycolipids, rhamnolipids, sophorolipids, trehalolipids, surfactin, lipopeptides & lipoproteins, lichenysin, fatty acids, phospholipids, and polymeric biosurfactants. These are amphiphilic biomolecules with lipophilic and hydrophilic ends and are used as drug delivery vehicles (foaming, solubilizer, detergent, and emulsifier) in the pharmaceutical industry. Despite additives, they have some biological activity as well (anti-cancer, anti-viral, anti-microbial, P-gp inhibition, etc.). These biomolecules possess better safety profiles and are biocompatible, biodegradable, and specific at different temperatures.

CONCLUSION

Biosurfactants exhibit good biomedicine and additive properties that can be used in developing novel drug delivery systems. However, more research should be driven due to the lack of comprehensive toxicity testing and high production cost which limits their use.

Sophorolipid Biosurfactant Can Control Cutaneous Dermatophytosis Caused by Trichophyton mentagrophytes

Trichophyton mentagrophytes, a zoophilic species, is one of the most frequently isolated dermatophytes in many parts of the world. This study investigated the efficacy of a sophorolipid (SL-YS3) produced by Rhodotorula babjevae YS3 against dermatophytosis caused by T. mentagrophytes. SL-YS3 was characterized by gas chromatography–mass spectrometry (GC–MS) and ultra-performance liquid chromatography, coupled with electrospray mass spectrometry (UPLC-ESI-MS). SL-YS3 comprised of six different fatty acids as the hydrophobic components of constituent congeners and sophorose as the hydrophilic component. Inhibitory effects of purified SL-YS3 against hyphal growth was found to be 85% at a 2 mg ml^–1 concentration, and MIC was 1 mg ml^–1. Microscopic examination with scanning electron microscopy (SEM), atomic force microscopy, and confocal laser scanning microscopy (CLSM) revealed that SL-YS3 exerts its effect by disrupting cell membrane integrity causing cell death. SL-YS3 was also effective in reducing the biofilms formed by T. mentagrophytes, which was observed spectrophotometrically with crystal-violet staining and further validated with SEM and CLSM studies of treated biofilms. In vivo studies in a mouse model of cutaneous dermatophytosis involving macroscopic observations, percent culture recovery from skin samples, and histopathological studies showed that SL-YS3 could effectively cure the infected mice after 21 days of topical treatment. Terbinafine (TRB) was used as a standard drug in the experiments. We demonstrate, for the first time, the antidermatophytic activity of a sophorolipid biosurfactant. The findings are suggestive that SL-YS3 can be formulated as a novel antifungal compound to treat cutaneous mycoses caused by T. mentagrophytes.

Mechanism-specific and whole-organism ecotoxicity of mono-rhamnolipids

Biosurfactants like rhamnolipids are promising alternatives to chemical surfactants in a range of applications. A wider use requires an analysis of their environmental fate and their ecotoxicological potential. In the present study mono-rhamnolipids produced by a recombinant Pseudomonas putida strain were analyzed using the Green Toxicology concept for acute and mechanism-specific toxicity in an ecotoxicological test battery. Acute toxicity tests with the invertebrate Daphnia magna and with zebrafish embryos (Danio rerio) were performed. In addition, microbial and fungicidal effectiveness was investigated. Mutagenicity of the sample was tested by means of the Ames fluctuation assay. A selected mono-rhamnolipid was used for model simulations regarding mutagenicity and estrogenic activity. Our results indicate that mono-rhamnolipids cause acute toxicity to daphnids and zebrafish embryos comparable to or even lower than chemical surfactants. Rhamnolipids showed very low toxicity to the germination of Aspergillus niger spores and the growth of Candida albicans. No frameshift mutation or base substitutions were observed using the Ames fluctuation assay with the two tester strains TA98 and TA100. This result was confirmed by model simulations. Likewise it was computed that rhamnolipids have no estrogenic potential. In conclusion, mono-rhamnolipids are an environmental friendly alternative to chemical surfactants as the ecotoxicological potential is low.

Development of novel sophorolipids with improved cytotoxic activity toward MDA-MB-231 breast cancer cells

Sophorolipids (SLs) are glycolipid biosurfactants, produced as a mixture of several compounds by some nonpathogenic yeast. In the current study, separation of individual SLs from mixtures with further evaluation of their surface properties and biologic activity on MDA-MB-321 breast cancer cell line were investigated. SLs were biosynthesized by Starmerella bombicola in a culture media supplemented with borage oil. A reverse-phase flash chromatography method with an automated system coupled with a prepacked cartridge was used to separate and purify the main SLs. Compositional analysis of SLs was performed by high-performance liquid chromatography with electrospray ionization mass spectrometry and tandem mass spectrometry. The following diacetylated lactonic SLs were isolated and purified: C18:0, C18:1, C18:2, and C18:3. The critical micelle concentration (CMC) and surface tension at CMC (γCMC ) of the purified SLs showed an increase with the number of double bonds. High cytotoxic effect against MDA-MB-231 cells was observed with C18:0 and C18:1 lactonic SLs. The cytotoxic effects of C18:3 lactonic SL on cancerous cells were for the first time studied. This cytotoxic effect was considerably higher than the promoted by acidic SLs; however, it induced a lower effect than the previously mentioned SLs, C18:0 and C18:1. To our knowledge, for the first time, C18:1 lactonic SL, in selected concentrations, proved to be able to inhibit MDA-MB-231 cell migration without compromising cell viability and to increase intracellular reactive oxygen species.

Sophorolipids Improve Sepsis Survival: Effects of Dosing and Derivatives

INTRODUCTION

Sophorolipids, a family of natural and easily chemo-enzymatically modified microbial glycolipids, are promising modulators of the immune response. We have previously demonstrated that sophorolipids mediate anti-inflammatory effects, including decreasing sepsis-related mortality at 36 h in vivo in a rat model of septic peritonitis and in vitro by decreasing nitric oxide and inflammatory cytokine production. Here we assessed the effect of sophorolipids on sepsis-related mortality when administered as a (1) single bolus versus sequential dosing and (2) natural mixture versus individual derivatives compared with vehicle alone.

METHODS

Intra-abdominal sepsis was induced in male, Sprague Dawley rats, 200 to 240 g, via cecal ligation and puncture. Sophorolipids (5-750 mg/kg) or vehicle (ethanol/sucrose/physiological saline) were injected intravenously (i.v.) via tail vein or inferior vena cava at the end of the operation either as a single dose or sequentially (q24 h x 3 doses); natural mixture was compared with select sophorolipid derivatives (n = 10-15 per group). Sham-operated animals served as nonsepsis controls. Survival rates were compared at 1 through 6 d post sepsis induction and tissue was analyzed by histopathology. Significance was determined by Kruskal-Wallis analysis with Bonferroni adjustment and Student's t-test.

RESULTS

Sophorolipid treatment at 5 mg/kg body weight improved survival in rats with cecal ligation and puncture-induced septic shock by 28% at 24 h and 42% at 72 h for single dose, 39% at 24 h and 26% at 72 h for sequential doses, and 23% overall survival for select sophorolipid derivatives when compared with vehicle control (P < 0.05 for sequential dosing). Toxicity was evident and dose-dependent with very high doses of sophorolipid (375-750 mg/kg body weight) with histopathology demonstrating interstitial and intra-alveolar edema with areas of microhemorrhage in pulmonary tissue when compared with vehicle controls (P < 0.05). No mortality was observed in sham operated controls at all doses tested.

CONCLUSIONS

Administration of sophorolipids after induction of intra-abdominal sepsis improves survival. The demonstration that sophorolipids can reduce sepsis-related mortality with different dosing regimens and derivatives provides continuing evidence toward a promising new therapy. Toxicity is evident at 75 to 150x the therapeutic dose in septic animals.

Sophorolipids block lethal effects of septic shock in rats in a cecal ligation and puncture model of experimental sepsis*

OBJECTIVE

Sophorolipids, a family of natural and easily chemoenzymatically modified microbial glycolipids, are promising modulators of the immune response. The potential of the therapeutic effect of sophorolipids was investigated in vivo in a rat model of sepsis and in vitro by analysis of nitric oxide and cytokine production.

DESIGN

Prospective, randomized animal study.

SETTING

Experimental laboratory.

SUBJECTS

Male Sprague-Dawley rats, 200-240 g.

INTERVENTIONS

Intra-abdominal sepsis was induced in vivo in 166 rats via cecal ligation and puncture (CLP); 60 rats were used to characterize the model. The remaining rats were treated with sophorolipids or vehicle (dimethylsulfoxide [DMSO]/physiologic saline) by intravenous (iv) tail vein or intraperitoneal (IP) injection immediately post-CLP (25/group). Survival rates were compared at 36 hrs after surgery. In vitro, macrophages were cultured in lipopolysaccharide (LPS) +/- sophorolipid and assayed for nitric oxide (NO) production and gene expression profiles of inflammatory cytokines. In addition, splenic lymphocytes isolated from CLP rats +/- sophorolipid treatment (three per group) were analyzed for cytokine production by RNase protection assay.

MEASUREMENTS AND MAIN RESULTS

CLP with 16-gauge needles optimized sepsis induction and resultant mortality. Sophorolipid treatment improved rat survival by 34% (iv) and 14% (IP) in comparison with vehicle controls (p < .05 for iv treatment). Sophorolipids decreased LPS-induced macrophage NO production by 28% (p < .05). mRNA expression of interleukin (IL)-1beta was downregulated by 42.5 +/- 4.7% (p < .05) and transforming growth factor (TGF)-beta1 was upregulated by 11.7 +/- 1.5% (p < .05) in splenocytes obtained 6 hrs postsophorolipid treatment. LPS-treated macrophages cultured 36 hrs with sophorolipids showed increases in mRNA expression of IL-1alpha (51.7%), IL-1beta (31.3%), and IL-6 (66.8%) (p < .05).

CONCLUSIONS

Administration of sophorolipids after induction of intra-abdominal sepsis significantly decreases mortality in this model. This may be mediated in part by decreased macrophage NO production and modulation of inflammatory responses.