The establishment of efficient bioconversion, extraction, and isolation processes for the production of phyllodulcin, a potential high intensity sweetener, from sweet hydrangea leaves (Hydrangea macrophylla Thunbergii).

INTRODUCTION: Hydrangea leaf tea has been traditionally consumed in the far-east Asian countries and is favoured for its distinct minty-sweet taste. Phyllodulcin is identified as a key sweet-tasting compound; it is 400-800 times sweeter than sucrose. However, its extraction has not been well-documented. In an effort to optimise phyllodulcin production, pretreatment processes to accumulate phyllodulcin as a final metabolite in leaf tissue were studied, and an efficient process was established for the extraction and purification of phyllodulcin. METHODS: Phyllodulcin was structurally identified using an LC/MS system. Hydrangea leaves were processed by either hand rolling or mechanical blending, by exposing them at different drying temperatures (25 and 70°C), and even by inducing bioconversion in leaf tissue. The leaf powder was extracted with various solvents (methanol, ethanol, and water) by soaking at 25°C for 12 h, ultrasonication at 35°C for 1 h or accelerated solvent extraction (ASE). Extracts were purified with ion exchange resins and purified using preparative HPLC. RESULTS: Traditional hand rolling and drying at 70°C significantly increased phyllodulcin accumulation in the leaves. Meanwhile, more phyllodulcin was obtained from the leaves blended mechanically or converted enzymatically compared to traditionally processed ones (P < 0.05). Methanol and ethanol were superior to water as extraction media, and the greatest phyllodulcin yields obtained by ASE, soaking and ultrasonication were 21.28, 21.20 and 19.33 mg/g, respectively, when methanol was used. Highly pure phyllodulcin powder was obtained with a yield of 2.12%. CONCLUSIONS: This promising result would be beneficial to the industrial utilisation of phyllodulcin as a potential high-intensity sweetener.

ß-Carotene inhibits neuroblastoma cell invasion and metastasis in vitro and in vivo by decreasing level of hypoxia-inducible factor-1α.

Neuroblastoma is the most prevalent extracranial solid tumor in childhood and has poor clinical outcome due to its high potential for metastasis. Consequently, an understanding of the mechanisms that modulate cancer cell invasion, migration and metastasis is important for the development of more effective chemotherapeutic agents. While ß-carotene is a vitamin A precursor that has been shown to exert antioxidant and anticancer effects, the anti-metastatic effects of ß-carotene on neuroblastoma cells remain poorly understood. The aim of the present study was to investigate the anti-metastatic effects of ß-carotene on highly malignant SK-N-BE(2)C neuroblastoma cells in vitro and in vivo. Treatment of SK-N-BE(2)C cells with ß-carotene was found to attenuate the migratory and invasive capabilities of the cells. In addition, the enzymatic activity and expression of matrix metalloproteinase (MMP)-2 was suppressed following ß-carotene treatment under both normoxia and hypoxia. To induce metastasis, immunodeficient nude mice were injected with SK-N-BE(2)C cells via the tail vein in vivo. The incidence of liver metastasis and mean tumor volume in mice that were administered ß-carotene was decreased compared to controls. Furthermore, mRNA levels of MMPs, membrane-type (MT) 2 MMP and tissue inhibitors of metalloproteinases in liver tumor tissues were also lower following ß-carotene treatment. Level of hypoxia-inducible factor-1α (HIF-1α) and its downstream targets, vascular endothelial growth factor and glucose transporter 1 (GLUT1), were lower both in vitro and in vivo following ß-carotene treatment. In conclusion, the present study provides the first evidence that ß-carotene may represent an effective chemotherapeutic agent by regulating the invasion and metastasis of neuroblastoma via HIF-1α.

Leaching characteristics of rare metal elements and chlorine in fly ash from ash melting plants for metal recovery.

In terms of resource recovery and environmental impact, melting furnace fly ash (MFA) is attracting much attention in Japan due to its high metal content. The study aims to obtain fundamental information on using a water extraction method not only to concentrate valuable rare metals but also to remove undesirable substances such as chlorine for their recovery from MFA. The composition and leaching characteristics of MFA was investigated. The results revealed that the metal content in MFA is nearly equal to raw ore quality. The content of Ag, In, Pd, Pb, and Zn is, in fact, higher than the content of raw ore. As for leaching behavior, Ag, Bi, In, Ga, Ge, Sb, Sn, and Te showed the lowest release at a neutral pH range. Pd was leached constantly regardless of pH, but its concentration was quite low. On the other hand, most of the Tl was easily leached, revealing that water extraction is not appropriate for Tl recovery from MFA. Major elements Cl, Ca, Na, and K, occupying about 70% of MFA, were mostly leached regardless of pH. Base metal elements Cu, Pb, and Zn showed minimum solubility at a neutral pH. The leaching ratio of target rare metal elements and base metal elements suggests that the optimal pH for water extraction is 8-10, at which the leaching concentration is minimized. The water extraction process removed most of the Cl, Ca, Na, and K, and the concentration of rare metals and base metals increased by four or five times.

Thermodynamic behavior of rare metals in the melting process of municipal solid waste (MSW) incineration residues.

This study aims to identify the thermodynamic behavior of rare metal elements during the melting process of municipal solid waste incineration residues. The fate of several selected rare metal elements was investigated using two approaches: experimental and thermodynamic equilibrium calculation at two actual melting plants. The results revealed that Ag, Bi, Ga, Ge, In, Pd, Sb, Te, and Tl are readily volatilized as chloride and/or gaseous forms and then condensed in melting furnace fly ash. On the other hand, Cr, Ni, Ta, V, and Zr tend to mostly remain in molten slag. Sn is volatilized as SnS (g) under reducing conditions while volatilization is suppressed under oxidizing conditions. Thermodynamically, total volatilization of Mn as MnCl2 (g) occurred with highly available chlorine under oxidizing conditions. However, at the actual plants, only a small proportion was volatilized. As for Co, Mo, and W, no volatilization occurred at the actual plants although the calculations suggest that these elements can form volatile metal chloride and volatilize. Non-equilibrium and heterogeneity of the actual plant melting furnace could explain the discrepancy. This study provided a good qualitative view of the behavior of rare metals in the melting process, but further investigation is required to produce a more accurate simulation and to resolve the discrepancy.