The anthranoid skeleton is believed to be formed by octaketide synthase (OKS), a member of the type III polyketide synthase (PKS) superfamily. Recombinant OKSs catalyze stepwise condensation of eight acetyl units to form a linear octaketide intermediate which, however, is incorrectly folded and cyclized to give the shunt products SEK4 and SEK4b. Here we report in vitro formation of the anthranoid scaffold by cell-free extracts from yeast-extract-treated Cassia bicapsularis cell cultures. Unlike field- and in vitro-grown shoots which accumulate anthraquinones, cell cultures mainly contained tetrahydroanthracenes, formation of which was increased 2.5-fold by the addition of yeast extract. The elicitor-stimulated accumulation of tetrahydroanthracenes was preceded by an approx. 35-fold increase in OKS activity. Incubation of cell-free extracts from yeast-extract-treated cell cultures with acetyl-CoA and [2-14C]malonyl-CoA led to formation of torosachrysone (tetrahydroanthracene) and emodin anthrone, beside two yet unidentified products. No product formation occurred in the absence of acetyl-CoA as starter substrate. To confirm the identities of the enzymatic products, cell-free extracts were incubated with acetyl-CoA and [U-13C3]malonyl-CoA and 13C incorporation was analyzed by ESI-MS/MS. Detection of anthranoid biosynthesis in cell-free extracts indicates in vitro cooperation of OKS with a yet unidentified factor or enzyme for octaketide cyclization.

The anthranoid skeleton is believed to be formed by octaketide synthase (OKS), a member of the type III polyketide synthase (PKS) superfamily. Recombinant OKSs catalyze stepwise condensation of eight acetyl units to form a linear octaketide intermediate which, however, is incorrectly folded and cyclized to give the shunt products SEK4 and SEK4b. Here we report in vitro formation of the anthranoid scaffold by cell-free extracts from yeast-extract-treated Cassia bicapsularis cell cultures. Unlike field- and in vitro-grown shoots which accumulate anthraquinones, cell cultures mainly contained tetrahydroanthracenes, formation of which was increased 2.5-fold by the addition of yeast extract. The elicitor-stimulated accumulation of tetrahydroanthracenes was preceded by an approx. 35-fold increase in OKS activity. Incubation of cell-free extracts from yeast-extract-treated cell cultures with acetyl-CoA and [2-14C]malonyl-CoA led to formation of torosachrysone (tetrahydroanthracene) and emodin anthrone, beside two yet unidentified products. No product formation occurred in the absence of acetyl-CoA as starter substrate. To confirm the identities of the enzymatic products, cell-free extracts were incubated with acetyl-CoA and [U-13C3]malonyl-CoA and 13C incorporation was analyzed by ESI-MS/MS. Detection of anthranoid biosynthesis in cell-free extracts indicates in vitro cooperation of OKS with a yet unidentified factor or enzyme for octaketide cyclization.

The anthranoid skeleton is believed to be formed by octaketide synthase (OKS), a member of the type III polyketide synthase (PKS) superfamily. Recombinant OKSs catalyze stepwise condensation of eight acetyl units to form a linear octaketide intermediate which, however, is incorrectly folded and cyclized to give the shunt products SEK4 and SEK4b. Here we report in vitro formation of the anthranoid scaffold by cell-free extracts from yeast-extract-treated Cassia bicapsularis cell cultures. Unlike field- and in vitro-grown shoots which accumulate anthraquinones, cell cultures mainly contained tetrahydroanthracenes, formation of which was increased 2.5-fold by the addition of yeast extract. The elicitor-stimulated accumulation of tetrahydroanthracenes was preceded by an approx. 35-fold increase in OKS activity. Incubation of cell-free extracts from yeast-extract-treated cell cultures with acetyl-CoA and [2-14C]malonyl-CoA led to formation of torosachrysone (tetrahydroanthracene) and emodin anthrone, beside two yet unidentified products. No product formation occurred in the absence of acetyl-CoA as starter substrate. To confirm the identities of the enzymatic products, cell-free extracts were incubated with acetyl-CoA and [U-13C3]malonyl-CoA and 13C incorporation was analyzed by ESI-MS/MS. Detection of anthranoid biosynthesis in cell-free extracts indicates in vitro cooperation of OKS with a yet unidentified factor or enzyme for octaketide cyclization.

The anthranoid skeleton is believed to be formed by octaketide synthase (OKS), a member of the type III polyketide synthase (PKS) superfamily. Recombinant OKSs catalyze stepwise condensation of eight acetyl units to form a linear octaketide intermediate which, however, is incorrectly folded and cyclized to give the shunt products SEK4 and SEK4b. Here we report in vitro formation of the anthranoid scaffold by cell-free extracts from yeast-extract-treated Cassia bicapsularis cell cultures. Unlike field- and in vitro-grown shoots which accumulate anthraquinones, cell cultures mainly contained tetrahydroanthracenes, formation of which was increased 2.5-fold by the addition of yeast extract. The elicitor-stimulated accumulation of tetrahydroanthracenes was preceded by an approx. 35-fold increase in OKS activity. Incubation of cell-free extracts from yeast-extract-treated cell cultures with acetyl-CoA and [2-14C]malonyl-CoA led to formation of torosachrysone (tetrahydroanthracene) and emodin anthrone, beside two yet unidentified products. No product formation occurred in the absence of acetyl-CoA as starter substrate. To confirm the identities of the enzymatic products, cell-free extracts were incubated with acetyl-CoA and [U-13C3]malonyl-CoA and 13C incorporation was analyzed by ESI-MS/MS. Detection of anthranoid biosynthesis in cell-free extracts indicates in vitro cooperation of OKS with a yet unidentified factor or enzyme for octaketide cyclization.

A phytochemical study of Geosmithia lavendula Pitt led to the isolation of three new anthraquinones: 1-acetyl-2,4,6,8-tetrahydroxy-9,10-anthraquinone (1), 2-acetyl-1,4,5,7-tetrahydroxy-9,10-anthraquinone (2), and 1-acetyl-2,4,5,6,7-pentahydroxy-9,10-anthraquinone (3), as well as another new compound named didodecyl thiodipropionate (propionic acid, 3,3-sulfinyl di-1,1'-didodecyl ester) (4), along with ten known compounds: 1-acetyl-2,4,5,7-tetrahydroxy-9,10-anthraquinone (rhodolamprometrin) (5), 1-acetyl-2,4,5,7,8-pentahydroxy-9,10-anthraquinone (6), (22E)-ergosta-6,22-diene-3β,5α,8α-triol, p-hydroxybenzyl alcohol, oleic acid, D-mannitol, palmitic acid, stearic acid, cis-vaccenic acid and 2-decenal. The structures of the isolated metabolites were elucidated based on NMR spectroscopic and mass spectrometric data. Compound 1 exhibited moderate activity against methicillin resistant Staphylococcus aureus with an IC50 value of 16.1 μg/mL.

A phytochemical study of Geosmithia lavendula Pitt led to the isolation of three new anthraquinones: 1-acetyl-2,4,6,8-tetrahydroxy-9,10-anthraquinone (1), 2-acetyl-1,4,5,7-tetrahydroxy-9,10-anthraquinone (2), and 1-acetyl-2,4,5,6,7-pentahydroxy-9,10-anthraquinone (3), as well as another new compound named didodecyl thiodipropionate (propionic acid, 3,3-sulfinyl di-1,1'-didodecyl ester) (4), along with ten known compounds: 1-acetyl-2,4,5,7-tetrahydroxy-9,10-anthraquinone (rhodolamprometrin) (5), 1-acetyl-2,4,5,7,8-pentahydroxy-9,10-anthraquinone (6), (22E)-ergosta-6,22-diene-3β,5α,8α-triol, p-hydroxybenzyl alcohol, oleic acid, D-mannitol, palmitic acid, stearic acid, cis-vaccenic acid and 2-decenal. The structures of the isolated metabolites were elucidated based on NMR spectroscopic and mass spectrometric data. Compound 1 exhibited moderate activity against methicillin resistant Staphylococcus aureus with an IC50 value of 16.1 μg/mL.

A phytochemical study of Geosmithia lavendula Pitt led to the isolation of three new anthraquinones: 1-acetyl-2,4,6,8-tetrahydroxy-9,10-anthraquinone (1), 2-acetyl-1,4,5,7-tetrahydroxy-9,10-anthraquinone (2), and 1-acetyl-2,4,5,6,7-pentahydroxy-9,10-anthraquinone (3), as well as another new compound named didodecyl thiodipropionate (propionic acid, 3,3-sulfinyl di-1,1'-didodecyl ester) (4), along with ten known compounds: 1-acetyl-2,4,5,7-tetrahydroxy-9,10-anthraquinone (rhodolamprometrin) (5), 1-acetyl-2,4,5,7,8-pentahydroxy-9,10-anthraquinone (6), (22E)-ergosta-6,22-diene-3β,5α,8α-triol, p-hydroxybenzyl alcohol, oleic acid, D-mannitol, palmitic acid, stearic acid, cis-vaccenic acid and 2-decenal. The structures of the isolated metabolites were elucidated based on NMR spectroscopic and mass spectrometric data. Compound 1 exhibited moderate activity against methicillin resistant Staphylococcus aureus with an IC50 value of 16.1 μg/mL.

A phytochemical study of Geosmithia lavendula Pitt led to the isolation of three new anthraquinones: 1-acetyl-2,4,6,8-tetrahydroxy-9,10-anthraquinone (1), 2-acetyl-1,4,5,7-tetrahydroxy-9,10-anthraquinone (2), and 1-acetyl-2,4,5,6,7-pentahydroxy-9,10-anthraquinone (3), as well as another new compound named didodecyl thiodipropionate (propionic acid, 3,3-sulfinyl di-1,1'-didodecyl ester) (4), along with ten known compounds: 1-acetyl-2,4,5,7-tetrahydroxy-9,10-anthraquinone (rhodolamprometrin) (5), 1-acetyl-2,4,5,7,8-pentahydroxy-9,10-anthraquinone (6), (22E)-ergosta-6,22-diene-3β,5α,8α-triol, p-hydroxybenzyl alcohol, oleic acid, D-mannitol, palmitic acid, stearic acid, cis-vaccenic acid and 2-decenal. The structures of the isolated metabolites were elucidated based on NMR spectroscopic and mass spectrometric data. Compound 1 exhibited moderate activity against methicillin resistant Staphylococcus aureus with an IC50 value of 16.1 μg/mL.

Nalidixic acid is practically insoluble in water therefore the aim of this study was to study the effect of both cosolvency and solid dispersionon its solubility. Among different cosolvents, the highest result was achieved by isopropanol (30% v/v). Through all studied solid dispersioncarriers in the ratio 1:1, sodium benzoate enhanced both the solubility and antibacterial activity of nalidixic acid and was therefore selected for further investigation. Increasing sodium benzoate ratio had significantly increased nalidixic acid solubility till a 1:8 ratio. Differential scanning calorimetry (DSC) showed a sharp endothermic peak of nalidixic acid which was slightly shifted to lower temperature accompanied by significant broadening in the case of solid dispersion. Further confirmation was obtained by X-ray powder diffraction (XRPD) whereas the peak heights were much reduced in the case of solid dispersion confirming the cause of increasing solubility.

Nalidixic acid is practically insoluble in water therefore the aim of this study was to study the effect of both cosolvency and solid dispersionon its solubility. Among different cosolvents, the highest result was achieved by isopropanol (30% v/v). Through all studied solid dispersioncarriers in the ratio 1:1, sodium benzoate enhanced both the solubility and antibacterial activity of nalidixic acid and was therefore selected for further investigation. Increasing sodium benzoate ratio had significantly increased nalidixic acid solubility till a 1:8 ratio. Differential scanning calorimetry (DSC) showed a sharp endothermic peak of nalidixic acid which was slightly shifted to lower temperature accompanied by significant broadening in the case of solid dispersion. Further confirmation was obtained by X-ray powder diffraction (XRPD) whereas the peak heights were much reduced in the case of solid dispersion confirming the cause of increasing solubility.