Supercritical fluid CO2 extraction of three polymethoxyflavones from Citri reticulatae pericarpium and subsequent preparative separation by continuous high-speed counter-current chromatography.

Polymethoxyflavones (PMFs) are widely found in Citri Reticulatae Pericarpium (CRP) and have been investigated with a broad spectrum of biological activities as well as health promoting properties. However, separation of the PMFs from a complex sample, especially preparative separation of these PMFs with high purity, remains challenging. In the present study, an efficient method based on supercritical fluid extraction (SFE) and continuous high-speed counter-current chromatography (HSCCC) has been developed for extracting and preparative purification PMFs from CRP. Various experimental conditions were investigated to optimize the SFE and HSCCC processes. Under these optimized conditions, crude extract of CRP (extract I) was obtained with a maximum contents of nobiletin, 3,5,6,7,8,3',4'-heptamethoxyflavone and tangeretin. Further extraction of crude extract I was carried out to obtain crude extract II, which was further isolated and purified by HSCCC. It was worth mentioned that continuous injection HSCCC process were realized without lost of separation efficiency, which allowed for multiple purification cycles and therefore saved a lot of labor and time. Furthermore, high-performance liquid chromatography (HPLC) was employed to analyze the fractions separated by HSCCC, which revealed that the purities of the three PMFs were all above 98%. The structures of the three PMFs were identified by LC-MS and 1H NMR spectroscopy.

Simultaneous separation of six pure polymethoxyflavones from sweet orange peel extract by high performance counter current chromatography.

Successful isolation of polymethoxyflavones (PMFs) from citrus peels has led to numerous evaluations of PMFs in a broad spectrum of biological activities, such as inhibition of chronic inflammation, cancer prevention and anti-atherogenic properties. Recent reports associated with the health promoting properties of PMFs in citrus fruits have dramatically increased. However, the limiting factor in animal and human study of PMFs is still the supply of pure PMFs, such as tangeretin, nobiletin, sinensetin and 3,5,6,7,3',4'-hexamethoxyflavone. Herein, we introduce the newly developed efficient separation method using high-performance counter-current chromatography (HPCCC) in isolating multiple pure single PMFs simultaneously in one cycle process. With the smallest preparation loop on the semi-preparative HPCCC instrument, the optimized solvent system of hexanes/ethyl acetate/methanol/water resulted in the isolation of pure sinensetin, tangeretin, nobiletin, 3,5,6,7,3',4'-hexamethoxyflavone, 5,6,7,4'-tetramethoxyflavone and 3,5,6,7,8,3',4'-heptamethoxyflavone directly from crude sweet orange peel extract in one cycle of separation process by HPCCC in the mode of reverse phase. The purity of each of the six isolated PMFs is greater than 96.6% analyzed by high-performance liquid chromatography and proton nuclear magnetic resonance. Scale-up and high purity of individual PMFs can be separated by using a large separation loop in preparative HPCCC model. The renovated HPCCC methodology can be practically used in natural product isolation and consequent biological property evaluation.

ICCLP: an inexact chance-constrained linear programming model for land-use management of lake areas in urban fringes.

Lake areas in urban fringes are under increasing urbanization pressure. Consequently, the conflict between rapid urban development and the maintenance of water bodies in such areas urgently needs to be addressed. An inexact chance-constrained linear programming (ICCLP) model for optimal land-use management of lake areas in urban fringes was developed. The ICCLP model was based on land-use suitability assessment and land evaluation. The maximum net economic benefit (NEB) was selected as the objective of land-use allocation. The total environmental capacity (TEC) of water systems and the public financial investment (PFI) at different probability levels were considered key constraints. Other constraints included in the model were land-use suitability, governmental requirements on the ratios of various land-use types, and technical constraints. A case study implementing the system was performed for the lake area of Hanyang at the urban fringe of Wuhan, central China, based on our previous study on land-use suitability assessment. The Hanyang lake area is under significant urbanization pressure. A 15-year optimal model for land-use allocation is proposed during 2006 to 2020 to better protect the water system and to gain the maximum benefits of development. Sixteen constraints were set for the optimal model. The model results indicated that NEB was between $1.48 x 10(9) and $8.76 x 10(9) or between $3.98 x 10(9) and $16.7 x 10(9), depending on the different urban-expansion patterns and land demands. The changes in total developed area and the land-use structure were analyzed under different probabilities (q ( i )) of TEC. Changes in q ( i ) resulted in different urban expansion patterns and demands on land, which were the direct result of the constraints imposed by TEC and PFI. The ICCLP model might help local authorities better understand and address complex land-use systems and develop optimal land-use management strategies that better balance urban expansion and grassland conservation.