• Assay of free ferulic acid and total ferulic acid for quality assessment of Angelica sinensis.

      Lu, Guang-Hua; Chan, Kelvin C.; Leung, Kelvin Sze-Yin; Chan, Chi-Leung; Zhao, Zhong-Zhen; Jiang, Zhi-Hong (2005)
      Activity of Chinese Danggui (DG), the processed root of Angelica sinensis (Oliv.) Diels, is linked to the ferulic acid content but the stability of ferulic acid during extraction for medicinal use is not known. The stabilities of ferulic acid and coniferyl ferulate were evaluated in the extracts of DG using a variety of extraction solvents. These included various combinations and proportions of methanol, water, formic acid, 1 M aqueous hydrochloric acid and 2% sodium hydrogen carbonate (NaHCO3) in water. Coniferyl ferulate was found liable to hydrolyze into ferulic acid in neutral, strongly acidic and basic solvents, where heat and water could facilitate this hydrolysis. However, the hydrolysis was relatively resisted in weakly organic acid. Based on the stability evaluation, two new terms, namely: free ferulic acid and total ferulic acid, were suggested and defined. Free ferulic acid refers to the natural content of ferulic acid in herbs. Total ferulic acid means the sum of free ferulic acid plus the amount of related hydrolyzed components. Meanwhile, the high-performance liquid chromatographic (HPLC) method was developed to assay free ferulic acid and total ferulic acid in DG using methanol-formic acid (95:5) and methanol-2% NaHCO3 in water (95:5) as extraction solvents, respectively. Ten DG samples were investigated on their contents of free and total ferulic acid. The results indicated that the amount variety of free ferulic acid was larger than that of their counterparts, and the ratio of total ferulic acid to free ferulic acid was 4.07 +/- 2.73 (mean +/- SD, n = 10). The chemical assay of DG using total ferulic acid content would be a better choice to assess the herbal quality and was recommended.
    • Determination of free and total available ferulic acid in different types of Chinese angelica by high performance liquid chromatography

      Lu, Guang-Hua; Leung, Kelvin Sze-Yin; Chan, Kelvin C.; Cheng, SiQi; Zhang, Hao; Zhao, Zhong-Zhen (Taipei City, Taiwan: Bureau of Food and Drug Analysis (BFDA), 2007)
      Free and conjugated forms of ferulic acid (FA) are generally available in higher plant taxa such as Chinese Angelica (CA, the roots of Angelica sinensis (Oliv.) Diels). These various forms of FA were found readily inter-convertible and the extractable level of each depended on solvent properties and acidity. Extraction efficiency using various pH solutions namely, water, 70% methanol, methanol-formic acid (95:5) and methanol-2% NaHCO3 in water (95:5) was compared. Extractable FA were found varying in samples under neutral solvents extraction, whilst relatively consistent for slightly acidic and alkali solvents which were therefore chosen as the optimal media to extract and determine the reproducible levels of free and total available FA. An accurate and rapid high performance liquid chromatographic (HPLC) analysis was conducted using an Alltima C18 column (5 mum, 4.6 mm i.d. x 250 mm) with a guard column (C18, 5 mum, 4.6 mm i.d. x 7.5 mm) at 30degreesC, eluted with a mixture of 1.0% acetic acid and acetonitrile in a gradient program at a flow rate of 1.0 mL/min and detected at 320 nm. Altogether 20 different types of CA samples including whole root, root head, rootlets, whole root slice, Angelica processed by Chinese yellow wine, and charred Angelica were quantified for free and total available FA. Total available FA was found more abundant than free counterpart with an average ratio of 3.15 (n = 20) in the range of 1.29 to 8.23 for these CA samples. The extraction protocol was proven reliable to quantitatively convert all conjugated FA into its free forms and thereby accurately determined by HPLC method for quality assessment.
    • Simultaneous qualitative and quantitative analyses of the major constituents in the rhizome of Ligusticum Chuanxiong using HPLC-DAD-MS.

      Yi, Tao; Leung, Kelvin Sze-Yin; Lu, Guang-Hua; Chan, Kelvin C.; Zhang, Hao (Tokyo: The Pharmaceutical Society of Japan, 2006)
      An HPLC-DAD-MS method was developed for the qualitative and quantitative analysis of the major constituents in Chuanxiong (the dried rhizome of Ligusticum chuanxiong Hort). Twenty compounds including phenolic constituents, alkylphthalides and phthalide dimers were identified using online ESI-MS and comparisons with literature data and standard compounds, and six of them were quantified by HPLC-DAD simultaneously. A comprehensive validation of the method including sensitivity, linearity, repeatability and recovery was conducted. The linear regressions were acquired with R(2) > 0.99 and limit of detection (LOD, S/N = 3) values were between 1.5 and 2.5 ng. The repeatability was evaluated by intra- and inter-day assays, and relative standard deviation (RSD) values were reported within 1.87%. The recovery studies for the quantified compounds were observed in the range of 96.36-102.37% with RSD values less than 2.63%. These phenolic constituents and alkylphthalides, the major constituents in Chuanxiong, are generally regarded as the index for the quality assessment of this herb. The overall procedure is accurate and reproducible, which is considered suitable for the qualitative and quantitative analyses of a large number of Chuanxiong samples.
    • Stone Deterioration in Polluted Urban Environments

      Mitchell, David J.; Searle, David E. (Science Publishers Inc., 2003)
      CONTENTS: . Stone Weathering and Urban Particulate Pollution in the UK: David E. Searle and David J. Mitchell . Urban Pollution and Stone Weathering in the Black Country: David E. Searle and David J. Mitchell . Potential for Building Stone Soiling from Vehicle-related Pollutants Along-side a Busy Road: Paul Giess and Vaughan Shilton . Weathering of Rocks by Lichens with Special Reference to Stonework: A Review: M.J. Wilson . Experimental Studies of Rock Weathering by Plant Roots: Updating the Work of Julius Sachs (1832-1897): D.N. Mottershead and H.A. Viles . Comparison of the Process of Decay of Two Limestones in a Polluted Urban Environment: A. Török . Initial Stages of Sandstone Decay in a Polluted Urban Environment: Alice V. Turkington . Role of NO2 and SO2 on the Degradation of Limestone: G.C. Allen et al. . Dry Deposition of SO2 on Carbonate Stone: An Overview of Laboratory Studies: Elizabeth A. Bede . Development and Potential Uses of Computer Simulation Techniques in the Study of Rock Weathering: Sarah Antill and Heather (H.A.) Viles . Comparative Assessment of Decay and Soiling of Masonry: Methodology and Analysis of Surveyor Variability: Jonathan Ball and Maureen E. Young . Colour Changes of Portland Stone: A Study of the Victoria and Albert Mu-seum Façade 1989-1998: Boris Pretzel . Representing Surface Loss on Gravestones: Does the Mean Mean Anything: Rob Inkpen et al. . Depth Profiling of Soluble Salts in Scottish Sandstone Buildings: Maureen E. Young and Pauline E. Cordiner . Local Variability of Marine Influence on Coastal Rock Weathering Rates: A Long-term Study: D.N. Mottershead . International Implications of Atmospheric Pollution on Stone: David J. Mitchell