New Sweet-Tasting Oleanane-Type Triterpenoid Saponins from “Tugancao” (Derris eriocarpa How)

With the aim to investigate the sweet-tasting compounds in Derris eriocarpa How (a substitute for licorice in “Zhuang” and “Dai” ethnopharmacy in Guangxi and Yunnan provinces of China) as well as to ascertain why the stem of D. eriocarpa can be used to substitute for licorice in the sweetness taste aspect, taste sensory-guided fractionation was conducted to isolate sweet constituents from the extract of D. eriocarpa. Four sweet-tasting triterpenoid saponins were obtained, including millettiasaponin A (<b>1</b>) and three new saponins named derrisaponins A–C (<b>2</b>–<b>4</b>). The sweetness potency was evaluated by a human sensory panel test. The sweetness intensities of compounds <b>1</b>–<b>4</b> were determined to be approximately 150, 80, 2, and 0.5 times relative to sucrose at the concentration of 1%, respectively, of which compounds <b>1</b> and <b>2</b>, with a free carboxyl group at the C-30 position, showed more potent sweetness intensity. In addition, compounds <b>1</b> and <b>2</b> showed no acute toxic activity at doses of 250 and 400 mg/kg of body weight, respectively, assessed through caudal vein injection to ICR mice. The contents of the sweetest compounds in stems were analyzed quantitatively as 352.80 mg/kg for compound <b>1</b> and 1887.60 mg/kg for compound <b>2</b> performed by ultra-performance liquid chromatography–tandem mass spectrometry

Direct Genetic and Enzymatic Evidence for Oxidative Cyclization in Hygromycin B Biosynthesis

Hygromycin B is an aminoglycoside antibiotic with a structurally distinctive orthoester linkage. Despite its long history of use in industry and in the laboratory, its biosynthesis remains poorly understood. We show here, by in-frame gene deletion <i>in vivo</i> and detailed enzyme characterization <i>in vitro</i>, that formation of the unique orthoester moiety is catalyzed by the α-ketoglutarate- and non-heme iron-dependent oxygenase HygX. In addition, we identify HygF as a glycosyltransferase adding UDP-hexose to 2-deoxystreptamine, HygM as a methyltransferase responsible for N-3 methylation, and HygK as an epimerase. These experimental results and bioinformatic analyses allow a detailed pathway for hygromycin B biosynthesis to be proposed, including the key oxidative cyclization reactions

New Sweet-Tasting C21-Pregnane Glycosides from Pericarps of Myriopteron extensum

Ten novel C21 pregnane glycosides, extensumside C–L (<b>1</b>–<b>10</b>), were isolated as highly sweet-tasting substances from the edible pericarps of Myriopteron extensum (Wight) K. Schum by sensory-guided fractionation and purification. Their structures were determined through 1D and 2D NMR, such as HSQC, HMBC, ¹H–¹H COSY, HSQC-TOCSY, and ROESY, as well as other spectroscopic analysis combined with chemical evidence. These compounds shared the same aglycone, 3β,16α-dihydroxy-pregn-5-en-20-one, and contained the deoxysugar chain and the glucose chain which were linked to C-3 and C-16 of the aglycone, respectively. The sweetness potency was evaluated by a human sensory panel test and preliminary structure–taste relationship was discussed. The sweetness intensities of these compounds are between 50 and 400 times greater than that of sucrose. Furthermore, quantitation analyses of compounds <b>1</b>, <b>3</b>, <b>4</b>, and <b>6</b> in different parts of M. extensum indicated that the concentrations of these sweet components in the pericarps are obviously higher than those in stems and roots

New Sweet-Tasting C21 Pregnane Glycosides from the Roots of <i>Myriopteron extensum</i>

To investigate the sweet-tasting components in the roots of <i>Myriopteron extensum</i>, the phytochemical study of its roots was conducted, which led to the discovery of 12 new C21 pregnane glycosides (extensumside M-X, <b>1</b>–<b>12</b>) and two known ones (extensumside C and extensumside E, <b>13</b>–<b>14</b>). Their chemical structure elucidation was accomplished by means of spectroscopic methods: IR, UV, ESI-MS, and NMR (¹H NMR, ¹³C NMR, HSQC, ¹H–¹H COSY, HMBC, HSQC-TOCSY, and ROESY), as well as the chemical evidence. Sensory analysis of these compounds revealed that nine of them (<b>1</b>, <b>3</b>, <b>4</b>, <b>5</b>, <b>6</b>, <b>7</b>, <b>8</b>, <b>13</b>, and <b>14</b>) are highly sweet-tasting compounds. Their sweetness intensities are 25 to 400 times greater than that of sucrose. Analysis of the structure–activity relationship (SAR) indicated that the sweet intensities of the isolated compounds are closely related to the aglycone 3β,16α-dihydroxy-pregn-5-en-20-one, the number and type of the monosaccharide in the sugar chain linked to C-3 and C-16 and the position of the mBe group

High-Purity Fatty Acid <i>n</i>‑Octyl Esters from Housefly (<i>Musca domestica</i> L.) Larval Lipids, a Potential New Biolubricant Source

With the cost of traditional lipid feedstocks constituting 70% of the total cost of biolubricant production, it is urgent to find a new lipid source for the biodiesel and biolubricant industry. With the elevated acid value (61.8 mg of KOH/g) of housefly larval lipids, converting the free fatty acid (FFA) into a biolubricant could serve as a value-added approach to the larval diesel industry, other than pretreatment by acid-catalyzed esterification for biodiesel production. This study developed a method of producing high-purity fatty acid <i>n</i>-octyl esters (FAOEs) from housefly (<i>Musca domestica</i> L.) larvae. The housefly larva free fatty acids (HLFFAs) from the larva lipids were obtained by wipe-film short-path distillation. FAOEs were produced by esterifying <i>n</i>-octanol with HLFFAs (catalyzed by benzenesulfonic acid under the following conditions: catalyst loading, 2 wt %; molar ratio of <i>n</i>-octanol to FFA, 3:1; temperature, 100 °C; time, 2 h). Excess <i>n</i>-octanol was effectively removed by high-vacuum (80 Pa) distillation at 90 °C. The unreacted FFAs were neutralized using demethylated crude glycerin, which is a byproduct of biodiesel production. A practical method of producing high-purity fatty acid <i>n</i>-octyl esters (99.19 wt %) derived from housefly larva lipids was thus developed, and the product could serve as a replacement for certain low-viscosity mineral lubricants such as liquid paraffin, polyalphaolefin 6, and SN 500