Lactone Form Research Articles

Effects of “mature micelle” formation of Pluronic P123 on equilibrium between lactone and carboxylate forms of 10-hydrocamptothecin in water

10-Hydrocamptothecin (HCPT) exists, like most of the antitumor drugs in the camptothecin (CPT) family, in the form of either lactone or carboxylate, but only the former with a closed E-ring has antitumor efficacy and the lactone fraction at physiological pH is quite low. Herein, we examined the effect of addition of an amphiphilic copolymer Pluronic P123 on HCPT in water. P123 is composed of major poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) and minor diblock copolymers. The lactone fraction of HCPT in the P123 aqueous solution was increased with the copolymer concentration, and the transition P123 concentration was higher than the critical micelle concentration by about two orders of magnitude and lower than critical gelation concentration by 1.5 orders of magnitude. We anticipated that the key event was the co-assembly between drug molecules and “mature micelles” instead of either physical gelation or merely the nascent micelle formation. Such anticipation was confirmed by the fluorescence anisotropy of HCPT at various P123 concentrations. We also explicitly indicated that the enhancement of the lactone fraction was not due to a kinetic delay of the ring-opening of drugs within micelles, but a thermodynamic shift of the equilibrium between the active and inactive forms driven by drug–material interactions. Further, the equilibrium constant (Kmicelle) of HCPT within P123 micelles was determined based on analysis of partition between micelles and their medium of both the lactone and carboxylate forms, by which we afforded the so-far only equilibrium constant of the CPT-family drugs within suspended nanoparticles.

Effects of amphiphilic block copolymers on the equilibrium lactone fractions of camptothecin analogues at different pHs.

Camptothecin (CPT) and its analogues constitute one of the most important families of anticancer drugs. However, the CPT-family members have to confront the severe problem of hydrolysis from lactone form, the only form capable of antitumor efficacy, to the carboxylate form, leading to a significant decrease in therapy efficiency as well as severe side effects. Herein, two CPT analogues with different water solubilities, 10-hydrocamptothecin (HCPT) and topotecan (TPT), and four poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEG-PPG-PEG, Pluronic) copolymers of varied hydrophilic-lipophilic balance (HLB) values, were examined with emphasis on the change of the equilibrium lactone fraction (flactone) of the drugs after addition of the copolymers. In all cases, flactone was enhanced. For weak water-soluble HCPT, the enhancement extent was significantly increased with decrease of the copolymer HLB, which is influenced by the block chain length for a given series of amphiphilic block copolymers. The effect was less significant for TPT, a more hydrophilic drug. The fluorescence experiments confirmed the assembly of the drugs into polymeric micelles. A series of pH titrations were also carried out, which quantified the shift of pH1/2 (pH when flactone = 0.5) after addition of the copolymers. The optimal or most sensitive pH, pHopt, which gave the maximum enhancement of flactone by the polymers, was found to depend upon the type of drug, the HLB value of copolymer, and also the polymer concentration. Hence, this work has indicated the universality of the enhancement effect of polymeric micelles on the equilibrium lactone fractions of CPT analogues, and meanwhile revealed the dependence of the enhancement extent upon the HLB values of the copolymer and hydrophilicity of the drug. The concept of optimal pH has also been put forward for the first time.

Bicarbonate Attenuates Irinotecan-Induced Cytotoxicity through Regulation of Both Extracellular and Intracellular <i>pHs</i> in Intestine Cell Line

The anti-cancer therapy of irinotecan (CPT-11) is often limited due to severe late-onset diarrhea. Because the higher toxic form of CPT-11/its active metabolite (SN-38) is produced at acidification, the usefulness of oral sodium bicarbonate treatment against the CPT-11/SN-38-induced intestinal injuries and diarrhea has been confirmed. However, the roles of bicarbonate have been suggested to affect not only intestinal pH environment but also intracellular pH and CPT-11/SN-38 dynamics. The present study proposed to clarify the hypothesis in CPT-11/SN-38-exposed colon cell line in various pH conditions adjusted by bicarbonate. HT29 cell pre-exposed to ~1.0 μM SN-38 lactone or carboxylate forms was incubated at different pH adjusted by either bicarbonate or HCl/NaOH. The degrees of SN-38-induced cell injury depended on the higher proportion of the toxic form (lactone) of SN-38 rather than mere pH condition of medium. Apoptosis and cell injury induced by SN-38 were significantly inhibited by bicarbonate in a dose-dependent manner. Intercellular pH acidification induced by SN-38 was significantly prevented by 30 mM bicarbonate. Cell cytotoxicity of SN-38 depended on not only extracellular but also intracellular pH that converts the SN-38 form, while the intracellular acidification was prevented by bicarbonate. The multiple regulations of bicarbonate on both exracellular and intracellular pH would be essential mechanism against intestinal cell injury by CPT-11/SN-38.

Degradation kinetics of monacolin K in red yeast rice powder using multiresponse modeling approach

The effects of storage temperature (4, 20, 30, 40, 50°C) and atmospheric conditions in packages (vacuum, atmospheric) on degradation kinetics of monacolin K, an antihypercholesterolemic agent, in red yeast rice powder were investigated using multiresponse modeling approach. Storage of red yeast rice powder at 4°C under vacuum package was found to enhance retention of monacolin K. Multiresponse modeling revealed degradation path of monacolin K acid form into their dehydromonacolin K and unknown product under vacuum package, while oxidized product was also formed under atmospheric package. Monacolin K lactone form and precursor were degraded into dehydromonacolin K lactone form, while degradation of dehydromonacolin K lactone form to unknown was more pronounced at temperature higher than 30°C. Oxidized product was also generated from monacolin K lactone form in atmospheric package. High activation energy of monacolin K degradation in acid form indicated that degradation of monacolin K to their dehydromonacolin K was more susceptible to temperature change as compared to lactone form.

Simply mixing with poly(ethylene glycol) enhances the fraction of the active chemical form of antitumor drugs of camptothecin family

This paper reveals a new function of poly(ethylene glycol) (PEG) – a common polymer in pharmaceutics – enhancement of the active chemical form of the antitumor drugs of camptothecin (CPT) analogs. All of members in the CPT family confront the severe problem of hydrolysis of the active lactone ring to the inactive carboxylate, leading to not only less efficiency but also more toxicity. Herein, we report that the equilibrium fraction of the active lactone form could be enhanced significantly by simply mixing the drug solution with PEG. For instance, while the equilibrium lactone fraction of topotecan (TPT) was only a bit more than 10% under neutral pH at 37°C, it was increased to nearly 50% in the presence of 40wt.% PEG. Two CPT family members, TPT and 10-hydrocamptothecin, and six PEG agents with molecular weight from 200 to 5000, were tested, and the phenomenon was confirmed to be universal. The underlying reason was further discussed. The in vivo drug efficacy was also observed in a solid tumor model in mice.

Simultaneous determination of lovastatin and citrinin in red yeast rice supplements by micellar electrokinetic capillary chromatography

Lovastatin is a main component of Monascus purpureus fermented red rice contributing to the lipid-lowering effect. Citrinin is a toxic fermentation by-product which can be found as a contaminant. An accurate, simple and rapid micellar electrokinetic capillary chromatographic method was developed for the first time for simultaneous determination of lovastatin present in lactone and hydroxy acid forms and citrinin in red rice products provided by different manufacturers and formulated in various dosage forms. Separation was achieved within only 2min using 20mM of phosphate buffer at pH 7.0 and 30mM of sodium dodecyl sulphate at an applied voltage of 25kV. Sensitivity crucial for detecting citrinin was enhanced by using an extended light path capillary. The results showed that the content of lovastatin and its acid form in dietary supplements were considerably different indicating the need for improved standardization in order to ensure efficiency and safety of these products.

Synthesis and characterization of 10-hydroxycamptothecin – sebacate – layered double hydroxide nanocomposites

10-Hydroxycamptothecin (HCPT) as a hydrophobic anticancer drug brings many challenges in the clinical applications due to its poor water solubility and the presence of a chemically unstable lactone ring. In this work, the nanocomposites of HCPT intercalated layered double hydroxide (LDH) were prepared by a secondary intercalation method, and the encapsulated HCPT could keep the biologically active lactone form. A Zn–Al–NO3 LDH was pillared with sebacate anions by a co-precipitation method in an aqueous medium, and then HCPT was intercalated into the LDH's gallery via hydrophobic interaction in an ethanol medium. The parallel alkyl chains of perpendicularly arranged sebacate anions in the LDH gallery provide a hydrophobic space for the drug intercalation. The in vitro release kinetics of HCPT from the nanocomposites could be fitted with the pseudo-second-order kinetic model, and the diffusion of HCPT through the LDH particles played an important role in controlling the drug release. The nanocomposites can be considered as a potential drug delivery system.

Synthesis of Water-Soluble Camptothecin–Polyoxetane Conjugates via Click Chemistry

Water-soluble camptothecin (CPT)-polyoxetane conjugates were synthesized using a clickable polymeric platform P(EAMO) that was made by polymerization of acetylene-functionalized 3-ethyl-3-(hydroxymethyl)oxetane (i.e., EAMO). CPT was first modified with a linker 6-azidohexanoic acid via an ester linkage to yield CPT-azide. CPT-azide was then click coupled to P(EAMO) in dichloromethane using bromotris(triphenylphosphine)copper(I)/N,N-diisopropylethylamine. For water solubility and cytocompatibility improvement, methoxypolyethylene glycol azide (mPEG-azide) was synthesized from mPEG 750 g mol(-1) and click grafted using copper(II) sulfate and sodium ascorbate to P(EAMO)-g-CPT. (1)H NMR spectroscopy confirmed synthesis of all intermediates and the final product P(EAMO)-g-CPT/PEG. CPT was found to retain its therapeutically active lactone form. The resulting P(EAMO)-g-CPT/PEG conjugates were water-soluble and produced dose-dependent cytotoxicity to human glioma cells and increased γ-H2AX foci formation, indicating extensive cell cycle-dependent DNA damage. Altogether, we have synthesized CPT-polymer conjugates able to induce controlled toxicity to human cancer cells.

Structural Spectroscopy and Dynamics of Inter- and Intramolecular H-Bonding Interactions of Topotecan, a Potent Anticancer Drug, in Organic Solvents and in Aqueous Solution

We report on the role of H-bonding interactions on the UV-visible absorption and emission (steady-state and time-resolved) spectroscopy of topotecan (TPT) in solution. In aprotic solvents, a very fast (less than 10 ps) excited-state intramolecular proton-transfer reaction occurs in the absorbing enol (E) form to give a zwitterion (Z) form, emitting with a large Stokes shift. In protic solvents like methanol, the time constant of Z* formation is longer (32 ps) due to the participation of solvent molecules in the proton-transfer reaction. In aqueous solution at near-neutral pH (6.24), a ground-state equilibrium is established between E, cation (C), and Z forms. Direct excitation of E leads to Z* through two channels: a very fast one (less than 10 ps) involving an intramolecular proton-tranfer and a slower one (680 ps) with the C* intermediate formation and reaction. A fast (42 ps) deprotonation of E* to give the excited anion (A*) also competes with the photoformation of Z* at the S(1) state. At pH =12.15, the A structures are the principal emitting species (τ(A) ~ 0.41 ns), showing the largest Stokes shift. In aqueous solutions, we cannot exclude the existence of an equilibrium between the lactone and carboxylate forms of TPT, whose spectroscopic (absorption and emission spectra) and dynamical behaviors should not be very different. Time-resolved emission anisotropy measurements in solvents of different viscosities suggest that the rotational relaxation time (φ) of TPT is mainly governed by the viscosity of the medium, increasing from 104 ps (in tetrahydrofuran, THF) to 156 ps (in water) and 338 ps (in dimethyl sulfoxide, DMSO). These results give spectroscopic and dynamical information on the structures, stability, and dynamics (picosecond to nanosecond time scale) of TPT in solution. They provide insights on the role of the intermolecular H-bonding surrounding medium on the ground- and excited-state structure and reaction of TPT. The finding should contribute to a better understanding of the relationship between the structures of the drug and its surroundings.

Pitavastatin: a different pharmacological profile

Pitavastatin, a synthetic HMG-CoA reductase inhibitor, is characterized by a cyclopropyl moiety that results in several pharmacological differences compared with other statins. These include inhibition of cholesterol synthesis and increased lipoprotein lipase expression at lower doses than other statins, and significant high-density and apolipoprotein A1-elevating activity that persists with time. Pitavastatin has a higher bioavailability (60%) than any other statin and the majority of the bioavailable fraction after oral dosing is excreted unchanged in the bile. The enterohepatic circulation of unchanged pitavastatin contributes to the prolonged duration of action, allowing once-daily, any-time dosing. Pitavastatin undergoes only minor metabolism by CYP2C9 but is not metabolized by CYP3A4. Neither pitavastatin nor its lactone form have inhibitory effects on cytochrome P450, and CYP3A4 inhibitors have no effect on pitavastatin plasma concentrations. Moreover, P-glycoprotein-mediated transport does not play a major role in the disposition of pitavastatin and pitavastatin does not inhibit P-glycoprotein activity. Pitavastatin is transported into the liver by several hepatic transporters, but organic anion-transporting polypeptide 1B1 inhibitors have relatively little effect on plasma pitavastatin concentrations compared with other statins. With the exception of multitransporter inhibitors, such as ciclosporin, interactions are generally of no clinical significance. As a result, pitavastatin has minimal drug–drug and drug–food interactions, making it a good treatment option in the large population of individuals with dyslipidemia who require multidrug therapy.

Investigation into the Efficacy of Val-SN-38, a Valine-Ester Prodrug of the Anti-Cancer Agent SN-38

We recently reported that Val-SN-38, a novel valine ester prodrug of SN-38, had greatly improved the intracellular accumulation of SN-38 in MCF-7 cell line, probably through enhanced uptake via amino acid transporters. In the present study, the efficacy of Val-SN-38 was further investigated both in vitro and in vivo. It was found that the in vitro cytotoxic effect of Val-SN-38 was similar to that of SN-38. Moreover, Val-SN-38 exhibited an equal potency to that of SN-38 in survival experiments in vivo. Because these results seemed to be contrary to the previous finding, further investigation was performed to find out the underlying cause of the contradiction. As only the lactone form is known to have cytotoxic activity, the proportion of lactone in Val-SN-38 and SN-38 was determined, but no differences were found. However, it turned out that Val-SN-38 had poor stability compared with SN-38, which resulted in a decrease in beneficial efficacy for Val-SN-38. Overall, the present study showed that a valine-added prodrug approach could be advantageous provided that the stability of the compound can be ensured. We believe this is a noteworthy study that unravels the discrepancy between intracellular accumulation and efficacy of valine-added prodrug.

Effect of levels of acetate on the mevalonate pathway of Borrelia burgdorferi.

Borrelia burgdorferi, the agent of Lyme disease, is a spirochetal pathogen with limited metabolic capabilities that survives under highly disparate host-specific conditions. However, the borrelial genome encodes several proteins of the mevalonate pathway (MP) that utilizes acetyl-CoA as a substrate leading to intermediate metabolites critical for biogenesis of peptidoglycan and post-translational modifications of proteins. In this study, we analyzed the MP and contributions of acetate in modulation of adaptive responses in B. burgdorferi. Reverse-transcription PCR revealed that components of the MP are transcribed as individual open reading frames. Immunoblot analysis using monospecific sera confirmed synthesis of members of the MP in B. burgdorferi. The rate-limiting step of the MP is mediated by HMG-CoA reductase (HMGR) via conversion of HMG-CoA to mevalonate. Recombinant borrelial HMGR exhibited a Km value of 132 µM with a Vmax of 1.94 µmol NADPH oxidized minute−1 (mg protein)−1 and was inhibited by statins. Total protein lysates from two different infectious, clonal isolates of B. burgdorferi grown under conditions that mimicked fed-ticks (pH 6.8/37°C) exhibited increased levels of HMGR while other members of the MP were elevated under unfed-tick (pH 7.6/23°C) conditions. Increased extra-cellular acetate gave rise to elevated levels of MP proteins along with RpoS, CsrABb and their respective regulons responsible for mediating vertebrate host-specific adaptation. Both lactone and acid forms of two different statins inhibited growth of B. burgdorferi strain B31, while overexpression of HMGR was able to partially overcome that inhibition. In summary, these studies on MP and contributions of acetate to host-specific adaptation have helped identify potential metabolic targets that can be manipulated to reduce the incidence of Lyme disease.

A two-step pH-dependent liquid–liquid extraction combined with HPLC-fluorescence method for the determination of 10-hydroxycamptothecin in mouse liver tissue

Context: Liquid–liquid extraction (LLE) shows high efficiency in the plasma sample preparation. However, this extraction method is not optimal for the biological samples containing complex organic interferences, such as liver and brain tissues. Some plant secondary metabolites can be converted between water-insoluble and water-soluble forms by pH adjustment.Objective: A two-step pH-dependent LLE method was introduced in this study to eliminate both water-soluble and lipidic interferences using the properties of pH-dependent interconvertible forms of analytes during sample preparation. A sensitive and reliable method using a reverse-phase HPLC coupled with a fluorescence detector was developed and validated.Materials and methods: 10-Hydroxycamptothecin (HCPT) with internal standard camptothecin and liver tissues were used as model compounds and biological samples. The lactone form of HCPT was converted to the water-soluble carboxylate form under moderate alkaline conditions, and the water-insoluble interferences were extracted with a nonpolar solvent. Afterward, the water-insoluble lactone form of HCPT was regenerated by acidification and then extracted using an organic solvent in a second LLE step.Results: The calibration curve was linear (r2 > 0.999) for HCPT concentrations ranging from 2.5 to 160 ng/mL. The mean recoveries of HCPT were 114.94 ± 3.98, 104.30 ± 2.44 and 95.90 ± 1.40% (n = 6) at concentrations of 2.5, 10 and 80 ng/mL, respectively. The stability determination data showed that no significant degradation occurred under the experimental conditions. This method was successfully applied to liver tissue distribution study of HCPT in mice.Discussion and conclusion: This two-step LLE can be applied to distribution studies of compounds with pH-dependent interconvertible forms in other biological matrices.

Jatropha oil and karanja oil as carbon sources for production of sophorolipids

AbstractBiosurfactants like sophorolipids (SL) are mild and environmentally friendly surfactants to be used in cosmetics and health care products. In addition to surfactant properties, SL also possess antimicrobial and skin healing properties. SL are produced by microbial fermentation using refined vegetable oils with glucose as a carbon source. This affects the economics of the production of SL. In the present work, non‐traditional oils like jatropha oil, karanja oil, and neem oil were used as newer feedstock for fermentative production of SL using Starmerella bombicola (ATCC 22214). In the fermentation, jatropha oil and karanja oil gave 6.0 and 7.6 g/L of SL (mainly lactonic form), respectively. HPLC, liquid chromatography–mass spectrometer, and 1H NMR of crude SL obtained from fermentation broth showed lactonic form of two major SL. Oleic acid and linoleic acid were preferentially consumed over other fatty acids by the organism. Neem oil gave lower yield, i.e., 2.63 g/L of SL (mainly acidic form).Practical applications: Jatropha oil and karanja oil are one of the non‐traditional oils grown wildly in India that have large potential that is still to be explored. These oils contain non‐glycerides components that exclude their use as edible oil. These oils can be used as substrate for SL that can find novel applications like in soil remediation, skin care production, antimicrobial agents, low foaming detergents, and food additives. The current study has provided proof of concept work that has indicated the potential of these oils to be used as substrate for SL. It has opened new avenues and there is further scope to improve the yield by validating the process parameters like aeration rate, residual substrate recycle and pH control.

Quantum chemical investigation of spectral-luminescent properties of zwitterion and lactone forms of rhodamine B

A quantum chemical software package based on a semiempirical INDO method with original spectroscopic parameterization is used to calculate the electronically excited states of lactone and zwitterion forms of rhodamine B. The rate constants of photophysical processes are estimated, and the fluorescence quantum yields are calculated. It is established that the wave function of the S 1 state in the zwitterion form is localized on the pyronin fragment and delocalized throughout the molecule in the lactone form.

Antitumor activities of emulsion electrospun fibers with core loading of hydroxycamptothecin via intratumoral implantation

Emulsion electrospinning was used in the present study to prepare core–sheath structured fibers with core-loading of hydroxycamptothecin (HCPT), and their antitumor activities were evaluated both in vitro on cancer cell lines and in vivo on tumor bearing mice via intratumoral implantation. Compared with our previous investigation on blend electrospun fibers, the addition of 2-hydroxypropyl-β-cyclodextrin (HPCD) and the preferential formation of HPCT/HPCD inclusion complexes resulted in significantly faster HCPT release from and higher degradation rate of emulsion electrospun fibers. The core–sheath structure led to around 93% of lactone form remaining after emulsion electrospinning and incubation in buffer solutions for over one month. In vitro cytotoxicity tests on HCPT-loaded electrospun fibers indicated over 20 times higher inhibitory activity against HepG2 cells than free HCPT during 72h incubation. Hepatoma H22 cells were subcutaneously injected into Kunming mice to form solid tumors for in vivo tests on the antitumor efficacy. Based on the tumor volume, survival rate and body weight changes, HCPT-loaded fibers indicated superior in vivo antitumor activities to and fewer side effects than free HCPT. The histopathological staining and immunohistochemical examinations of caspase-3 expression indicated more necrosis and apoptosis induced by HCPT-loaded fibers. The above results demonstrate the potential use of emulsion electrospun fibers as drug carriers for local treatment of solid tumors.

Camptothecin nanocolloids based on N,N,N-trimethyl chitosan: Efficient suppression of growth of multiple myeloma in a murine model

Camptothecin (CPT) exhibits very strong antitumor effects by inhibiting the activity of DNA topoisomerase I, but its application is greatly limited due to its low solubility and the instability of the active lactone form. To overcome these shortcomings, in the present study, we prepared novel camptothecin nanocolloids based on N,N,N-trimethyl chitosan (CPT-TMC) to efficiently and safely administer CPT systemically. Herein, we investigated the antitumor activity of CPT-TMC against a murine Balb/c myeloma model. Our results showed that CPT-TMC more effectively inhibited tumor growth and prolonged survival time than CPT in vivo, but no statistical difference was observed in vitro between CPT-TMC and CPT. These findings suggest that N,N,N-trimethyl chitosan could increase the stability and the antitumor effect of CPT and CPT-TMC is a potential approach for the effective treatment of multiple myeloma.

Experimental and theoretical spectroscopic and structural study of A-ring substituted camptothecins

Abstract The molecular architecture design and physical properties of seven camptothecin (CPT) alkaloids, structurally related to irinotecan (CPT-11), substituted with the cyclic bulk N-aliphatic substituents at A-ring as well as their different protonated forms were studied. The correlation between the molecular geometry and physical properties of the neutral lactone form and different possible cationic forms was elucidated, using the electronic absorptions (EAs), circular dichroic (CD) and Raman spectroscopy within the far -IR region as well as electrospray ionization and matrix-assisted laser desorption/ionization mass spectrometry and nuclear magnetic resonance methods. The electronic structures, and properties of the neutral CPTs, their mono- and diprotonated forms as well as molecular ion fragments, obtained by the mass spectrometric data are predicted theoretically using the DFT method.

Involvement of Specific Transport System on Uptake of Lactone Form of SN-38 in Human Intestinal Epithelial Cell Line Caco-2

The aim of this study was to elucidate the characteristics of the transport of lactone and carboxylate forms of SN-38 (SN-38L and SN-38C, respectively), a metabolite of irinotecan hydrochloride (CPT-11), with the human intestinal epithelial cell line, Caco-2. We examined SN-38L and SN-38C uptake from the apical side into Caco-2, and the effects of various compounds on the uptake of SN-38L. SN-38L and SN-38C in the cells were determined by HPLC with a fluorescence detector. When either SN-38L (0.5 µM) or SN-38C (0.5 µM) was added extracellularly at 37°C, the accumulation of SN-38L into the cells was about 10-fold higher than that of SN-38C, suggesting a dominant role of the lactone form in the uptake of SN-38 into Caco-2. The accumulation of SN-38L in Caco-2 increased time-dependently up to 10 min at 37°C, whereas the accumulation markedly decreased at 4°C. The initial uptake rate of SN-38L approached saturation at high concentrations with Michaelis-Menten constant and 'Hill coefficient,' 2.84±1.00 μM and 2.13±1.14, respectively (mean±S.E.). The accumulation of SN-38L was markedly inhibited by baicalin, an active ingredient of a Chinese herbal medicine, Hange-Shashin-To, as well as CPT-11. The type of inhibition by baicalin was competitive. In contrast, concomitant sulfobromophthalein, taurocholate and estrone 3-sulfate significantly increased SN-38L uptake. These results suggest that apical uptake of SN-38 by Caco-2 is dominantly performed as a lactone form through a specific transporter, which is competitively inhibited by baicalin.

Enhanced Production of Bioactive Sophorolipids by <i>Starmerella bombicola</i> NRRL Y-17069 by Design of Experiment Approach with Successive Purification and Characterization

In present study, fermentative production of Sophorolipids (SLs) by Starmerella bombicola NRRL Y-17069 that have antibacterial activities was optimized. The media components like glucose, yeast extract and urea were critical components in the microbial growth and formation of SL moiety. The secondary carbon; oleic acid supports the formation of SLs. These components were optimized for maximum production of total SLs which have potential application. Optimization by one factor at-a-time method, glucose and yeast extract were found to be best sources for maximum production of SLs (g/L), 20.94 and 32.1 resp. Oleic acid (100 g/L) gave maximum production of 54.16 g/L with 54 % conversion of added oleic acid in fermentation media indicating fed batch operation is best for SLs production. Total sophorolipids formed were purified and 98.1% lactonic form was obtained by crystallization. Characterization of lactonic SLs by FT-IR, NMR and attached fatty acid moiety was confirmed by GCMS.