Dear Editor: November 11, 2010
Enclosed is a manuscript by Chiang HM, Lin YT, Hsiao PL and Wen KC, entitled “Determination of Total Polyphenol Glycosides in Alo”. The paper is submitted to be considered for publication in your journal. This manuscript is original and not being considered elsewhere.
In recent years, using Chinese medicine is growing worldwide, so the quality and quantity control would be more important. In addition, a rapid and simple quantitation method was required. I hope this paper is acceptable for the publication in Journal of Food and Drug analysis.
Thank you for your attention to our paper! Correspondence about the paper should be directed to me at the following address
School of Cosmeceutical
China Medical University
Taichung, Taiwan 404
R. O. C.
Tel: 04-22053366 ext 5302
Determination of Total Polyphenol Glycosides in Aloe
HSIU-MEI CHIANG1, YA-TZE LIN2, PEI-LING HSIAO1 AND KUO-CHING WEN1* 1 Department of Cosmeceutics, China Medical University, Taichung, Taiwan.
2Food and Drug Administration, Department of Health, Executive Yuan, Taipei, Taiwan.
This article proposes an optimum hydrolysis condition and a gradient chromatographic method for the analysis of aloe extract and the hydrolysates. Polyphenol glycosides are reported to be hydrolyzed to lower polar aglycones and then become absorbable in intestine. It would be more reasonable if the total glycosides of active ingredients could be assayed. In this study, the contents of polyphenol glycosides in aloe, a common Chinese medicine and used as cosmetic, was studied. The contents of aglycones were determined in decoctions of the herb before and after hydrolysis. The aglycones assayed were aloin and aloe-emodin for aloe. The linearity (r>0.9997) and validation (<10%) of the calibration curves were excellent. The amount of aloin was 76.1±5.9 μmol/g in decoction and 77.7 ± 2.8 μmol/g in hydrolyasate; the amount of aloe-emodun was 8.3 ± 0.5 μmol/g in decoction and 8.1 ± 0.3 μmol/g in hydrolysate. The contents of aloin and aloe-emodin in aloe showed no significant difference prior to and after hydrolysis. This result may due to aloe was processed and the alycosides had transfer to aglycones. The method in this study can be applied to the determinations of the contents of aglycones and their glycosides in these Chinese herbs for quality control.
Key words: aloe, aloe-emodin, aloin, Chinese medicine, hydrolysis, HPLC
Aloe, dried leaf gel of Aloe ferox Mill. (Liliaceae), was an herb and Chinese medicine used to prevent cardiovascular diseases, cancer, neurodegeneration and diabetes.20 It is also used extensively by the cosmetic industry for its anti-inflammatory and wound and burn healing effects.21 (Jia et al., 2008). The major components of aloe are anthraquinones which include aloin (10-glucopyranosyl-1,8-dihydroxy-3-(hydroxymethyl)-9(10H)-anthracene; Figure 1), aloe-emodin (Figure 1), chrysophanol and aloinoside A and B(5). Aloin, found in nature as a mixture of two diasteromers, is an anthrone glycoside and contained in the exudate seeping from the freshly cut leaves. The leaves are used to treat asthma, gastrointestinal ulcers, cardiovascular disease, tumors, burns and diabetes, and aloe is also used in cosmetics for its anti-tyrosinase and anti-inflammatory effects(5-7).
Polyphenols such as flavonoids, anthraquinones, lignan, and aromatic acids were widely distributed in herbs, vegetables and fruits; they were found predominantly exist naturally as glycosides. It had been reported that polyphenols associated with many bioactivities related to antioxidants activity,1 prevention of cardiovascular disease,2-6 and anti-tumor activity7,8 . The pharmacokinetics of polyphenols have been clarified in recent years, and it is now known that the glycosides are hydrolyzed to more hydrophobic aglycones by enzymes or enteral bacteria and then absorbed.10-12 In the literature, it has been reported that most polyphenols, such as daidzein13, are predominantly excreted through body circulation with conjugated metabolites (sulfates/glucuronides), and only a few of them were present in the parent form. In addition, hydrolysis by acid or enterbacter in intestine would significantly elevate the contents of aglycones in decoction.
Yimei Jia a,∗, Guodong Zhaoa,b, Jicheng Jia. Preliminary evaluation: The effects of Aloe ferox Miller and Aloe arborescens Miller on wound healing. Journal of Ethnopharmacology 120 (2008) 181–189
Thornfeldt, C. 2005. Cosmeceuticals containing herbs: fact, fiction, and future. Dermatol. Surg. 31, 873-880; discussion 880.
Loots, du T., van der Westhuizen, F. H. and Botes, L. 2007. Aloe ferox leaf gel phytochemical content, antioxidant capacity, and possible health benefits. J. Agric. Food Chem. 55: 6891-6896.
Akev, N., Turkay, G., Can, A., Gurel, A., Yildiz, F., Yardibi, H., Ekiz, E. E. and Uzun, H. 2007. Tumour preventive effect of Aloe vera leaf pulp lectin (Aloctin I) on Ehrlich ascites tumours in mice. Phytother. Res. 21: 1070-1075.
Maenthaisong, R., Chaiyakunapruk, N., Niruntraporn, S. and Kongkaew, C. 2007. The efficacy of aloe vera used for burn wound healing: a systematic review. Burns 33: 713-718.
Dal'Belo, S. E., Gaspar, L. R. and Maia Campos, P. M. 2006. Moisturizing effect of cosmetic formulations containing Aloe vera extract in different concentrations assessed by skin bioengineering techniques. Skin Res. Technol. 12: 241-246.
Nagaoka, S., Fujii, A., Hino, M., Takemoto, M., Yasuda, M., Mishima, M., Ohara, K., Masumoto, A., Uno, H. and Nagashima, U. 2007. UV protection and singlet oxygen quenching activity of aloesaponarin I. J. Physical Chem. B 111: 13116-13123.
Reuter, J., Jocher, A., Stump, J., Grossjohann, B., Franke, G. and Schempp, C.M. 2008. Investigation of the anti-inflammatory potential of Aloe vera gel (97.5%) in the ultraviolet erythema test. Skin Pharmacol. Physiol. 21, 106-110.
It is complicated to determine the amount of each compound in an herb, because of not less than 30 active components exist in it. Thus, some indexes of quality control such as chromatographic fingerprints have been used in the past years. But it is not known how well those methods reflect the bioactivity of Chinese herbs. Measuring the specific components would make it easy to calculate the contents. For example, quantitative analysis of flavonoid aglycones in Ginkgo biloba products determined that the aglycone of isorhamnetin, quercetin and kaempferol24 and the total flavonoids cannot be less than 24%. Until now, quality control of Chinese medicine has been lenient in most countries since assays for only one glycoside or aglycone have been required. For example, the content of baicalin in Scutellariae Radix should not be less than 10% according to the Japanese Pharmacopeia.25 Furthermore, according to the Chinese Pharmacopeia, the content of barbaloin in Aloe barbadensis Miller should be more than 18% and aloin in Aloe ferox Miller not less than 6%.26 It is more appropriate to use the amount of total glycosides of these polyphenols as a standard for quality control of Chinese herbs, since most of the glycosides are assimilated with the aglycone form after oral administration.27
In this study, the amounts of aloin and aloe-emodin in Aloe was determined by HPLC with a UV-VIS detector before and after acid hydrolysis. This study was aimed at developing of a quantitative method for absorbable glycosides of these herbs.
MATERIALS AND METHODS
Aloe ferox was a kind gifts sponsored by a Chinese medicine company. Aloe-emodin, aloin, ascorbic acid and 6,7-dimethoxycoumarin (6,7-DMC) were purchased from Sigma Chemical Co. (St. Louis, MO, U.S.A.). Acetonitrile, methyl alcohol and ethyl acetate were purchased from J. T. Baker, Inc. (Phillipsburg, NJ, U.S.A.). Ortho-phosphoric acid was from Riedel-deHaën AG (Seelze, Germany). All the solvents used in this study were HPLC grade and Milli-Q plus water (Millipore, Bedford, MA, USA) was used throughout this study.
II. Sample Preparation
The decoction of aloe was prepared according to the standard decoction method (Wen, 2000). Briefly, 20 g of the crude drugs were weighed and pulverized, and then soaked with 400 mL of water. After that, the mixtures were boiled to 200 mL. The decoctions were then concentrated to 0.4 g/mL by vacuum-drying at 45℃ and aliquots were stored at -20℃ until used.
III. Investigation of Hydrolysis Conditions
Equal volume of HCl (1.2 N) and aloe decoction was mixed, and the mixtures were heated in a water bath at 80℃ for 0.5, 1, 2, 4, or 6 h, respectively. After extraction by an equal volume of ethyl acetate, the extraction was dried by nitrogen gas. The residue was dissolved in methanol and spiked with the internal standard for HPLC analysis.
Concentration of HCl
Five hundred microliters of 1.2 N HCl was added into 500 μL of decoction, 2.4 N HCl was added into another 500 μL of decoction, and the mixtures were heated in a water bath (80℃) for 1 h. The mixtures were extracted with ethyl acetate, and the process described above was repeated.
Equal volume of HCl (1.2 N) and aloe decoction was mixed,, and the mixtures were heated in a water bath at 80℃ or 100 ℃ for 1 h. The mixtures were extracted with ethyl acetate, and the process described above was repeated.
The Protective Effect of Ascorbic Acid
Five hundred microliters of HCl (1.2 N) and ascorbic acid (100, 50 or 0 mg/mL) were added into 500 μL of decoction. Each mixture was heated in a water bath (80 ℃) for 1 h. The mixtures were extracted with ethyl acetate, and the process described above was repeated.
The Effect of Light
Five hundred microliters of HCl (1.2 N) was added into 500 μL of decoction. The test tubes containing the mixture were either wrapped with aluminum foil to protect them from light or left unwrapped. The mixtures were heated and extracted as described above.
IV. HPLC Apparatus and Condition
HPLC analysis was performed on a Shimadzu HPLC system, equipped with a pump (LC-10AT vp, Shimadzu, Japan), an automatic injector (SPD-10AF, Shimadzu, Japan), a UV-VIS detector (SPD-10A vp, Shimadzu, Japan), a degasser (ERC-3415, Japan) and an Apollo C18 5μ column (4.6 × 250 mm, Alltech Associates, Inc. U.S.A.) maintained at ambient temperature. The mobile phase consisted of acetonitrile (A) and 0.1 % aqueous phosphoric acid (B) using a gradient elution of 24% A at 0-12 min, 24-50% A at 12-22 min, 50-24% A at 22-40 min and 24% A at 40-50 min. The flow rate was 1.0 mL/min and the detection wavelength was 254 nm. The injection volume was 20 μL.
For the determination of polyphenols in aloe, aloe-emodin and aloin were individually dissolved in methanol and diluted in series to 6.25-200 μg/mL for aloin, and 62.5-200 μg/mL for aloe-emodin as standard solutions. 6,7-DMC (50.00 μg/mL) was spiked into each standard solution as the internal standard. The calibration curves were constructed by plotting the peak area ratios of each standard to the internal standard versus concentration of each standard. Based on the calibration curves, the linear regressions and correlative coefficients were determined.
(2) Precision and Accuracy
Measurements of interday and intraday variability were utilized to assess the reproducibility and repeatability of this HPLC method. The intraday assays were determined by quantifying three replicates on the same day; the interday assays were carried out on three consecutive days. The real concentrations were calculated from standard curves and used to calculate the standard deviation (S.D.) and coefficient of variation (C.V.), used as indexes for precision and relative error for accuracy.
LLOQ (lower limit of quantification) represents the lowest concentration of analyte in a sample that can be determined with acceptable precision and accuracy, whereas LOD (limit of detection) represents the lowest concentration of analyte in a sample that can be detected (S/N > 3).
Three concentrations of the calibration standard were individually spiked into the decoction and assayed by HPLC. The recoveries were determined by the percentage of calculated concentration versus theoretical concentration.
The selective of the method was determined by standards and samples analysis. The peaks of aloe-emodin and aloin were identified by comparing the retention times and UV spectra with those of the standards.
The differences among the various hydrolysis conditions were compared by ANOVA with Scheffect’s test.
RESULTS AND DISCUSSION
HPLC chromatograms of aloin, aloe-emodin, decoction and hydrolasate of aloe were shown inFigure. 2A-C, respectively. Aloin and aloe-emodin of aloe in decoctions as well as the internal standard were well resolved within 40 min by gradient elution. The retention time of aloin was 17.0 min, that of 6,7 DMC was 19.2 min and that of aloe-emodin was 34.6 min. The linear regressions and concentration ranges of the standard curves for aloe are shown in Table 1. The calibration curves were linear in the range of 12.5 to 200 µg/mL for aloin and 6.25 to 200 µg/mL for aloe-emodin. Regression equation and correlation coefficients (r) were not less than 0.9997) showing a good linearity response for this quantitation method. A signal-to-noise ratio (S/N) of 3 and 10 was considered as the limit of detection (LOD) and the lower limit of quantification (LLOQ). The LOD was 0.5 µg/mL for aloin and 0.2 µg/mL for aloe-emodin; theLLOQ was 12.5 µg/mL for aloin and 6.25 µg/mL for aloe-emodin. These results indicated that the proposed method exhibits a good sensitivity.
The intraday and interday analytical precision and accuracy of these standard compounds are shown in Table 2. Validation of this assay method indicated that all coefficients of variation (CV) for intraday and interday analysis were less than 5%, and the relative errors were below 10%; the variations of the relative errors became more significant while the concentrations of standards decreased. The recoveries are shown in Table 3. The recoveries were 76.4-94.1% for aloin and 82.8~110.3% for aloe-emodin in aloe.
The contents of the two polyphenols in decoctions of various hydrolysis conditions are shown in Figures 3. In Figure 3D, ascorbic acid did not exhibit a notable protective effect on these compounds in aloe. In addition, when the hydrochloric acid concentration and heating temperature increased, the contents of anthraquinones decreased (Figure 3B, C). Furthermore, the aloe-emodin content decreased as the heating time increased (Figure 3A). We speculate that various anthrone-glycoside-derivatives would cleave into aglycone, and the results after hydrolysis of the same components in different preparations could differ.
Tables 4 show the contents of constitutes of aloe before or after acid hydrolysis. The amounts of aloin (76.1±5.9 µmol/g) and aloe-emodin (8.3±0.5 µmol/g) in the aloe decoction did not increase significantly after acid hydrolysis. Aloe sold in the retailer was processed. Aloin and aloe-emodin were present largely as aglycones in aloe, and the contents were similar to those of aloe hydrolysate, which might be due to the cleaving of the sugar moiety by heat during processing.26 This result was consistent to our previous study, emodin and physcion in crude Polygoni multiflori radix was increase after hydrolysis, but in processed Polygoni multiflori radix, the two anthraquinones shown no significant difference between decoction and hydrolysate (Chiang et al., 2007). The active components exist in Chinese medicine predominant in glycoside form, but the glycosides will hydrolyzed to the corresponding aglycones after acid or bacteria hydrolysis (Chiang et al., 2009).
Hence many polyphenol standards are not commercially available, Chinese herbs have been assessed quantitatively by only one glycoside or aglycone, which would not reflect real efficacy in vivo. However, the bioavailability of some aglycones in Chinese medicine may be over 100% due to the deglycosylation from glycosides in the gastrointestinal tract. For most crude Chinese herbs, polyophenols exist mainly in glycosides, especially in O-glycosides, and the amount of alycones increases noticeably after processed involving hydrolysis by acid or enzymes. Most of them are susceptible to absorption in aglycone form.32,33 The effect of enzymes is more specific, and the effect of acid is rapid and stronger. In the previous study, Polygoni multiflori radix and rhubarb decoction were incubated with acid or rat feces to cleave the sugar moiety from anthraquinones glycosides; this study demonstrated that both acid hydrolysis and feces incubation could convert anthraquinone-glycosides to aglycones.16,27 In addition, fermentation of Puerariae radix by Bifidobacterium breve would cleavage the glycosides to aglycones (Wen et al., 2010). Therefore, measuring the total contents of glycosides and their corresponding aglycones is helpful for understanding the fate of these polyphenols in body systems.27
The establishment of a simple, rapid and accurate quantitative method is important for quality control of Chinese medicine. For processed herbs such as aloe, the amount of aglycones could be measured directly before hydrolysis.27 In this study, a simple, economical, and efficient hydrolysis condition and HPLC methods were developed for polyphenol-rich herbs or formulation.
This work was supported by the Committee of China Medicine Pharmacy (CCMP95-RD-021) and China Medical University (CMU-95-099), Taiwan.
Hsu, C.-Y.; Chan, Y.-P.; Chang, J. Biol. Res.2007, 40, 13.
Figure Legends Fig. 1. Chemical structures of compounds detected in this study. A: Aloin and B: Aloe-emodin.
Fig. 2 HPLC chromatogram of Aloe ferox Miller decoction and its hydrolysate. A. Standard, B. in Aloe ferox Miller decoction and C. in Aloe ferox hydrolysate.
1. aloin 2. aloe-emodin IS: 6,7-DMC
Fig. 3 Histograms of aloe-emodin and aloin contents in Aloe ferox Miller decoction after acid hydrolysis.
A: the time effect on acid hydrolysis; B: the influence of hydrogen chloride concentration on acid hydrolysis; C: the temperature effect on acid hydrolysis D: the protection of constituent content with or without ascorbic acid and E: the influence of light on constituents.
Table 1. The regression equations, concentration ranges and correlation coefficients of constituents in Aloe ferox Miller
Conc. Range (g/mL)
Correlation coefficient (r)
Table 2. Intraday and interday analytical precision and accuracy of the constituents in aloe
Mean ± S.D. (C.V. %)
Mean ± S.D. (C.V. %)
201.28± 0.28 (0.14)
201.32 ±0.49 (0.24)
97.61 ± 0.56 (0.57)
97.5 0± 1.00 (1.03)
48.59 ± 0.49 (1.00)
48.86 ± 0.41 (0.85)
26.58 ± 0.44 (1.67)
26.09 ± 0.42 (1.59)
13.42 ± 0.65 (4.82)
13.73 ± 0.44 (3.22)
200.70 0.28 (0.14)
200.69 0.80 (0.40)
98.88 1.20 (1.22)
98.54 1.49 (1.51)
49.29 0.34 (0.68)
49.97 1.12 (2.24)
25.27 0.08 (0.32)
25.13 0.27 (1.07)
12.89 0.37 (2.90)
12.77 0.49 (3.83)
6.77 0.26 (3.86)
6.65 0.63 (9.49)
Table 3. Recoveries (%) of constituents from Polygonum cuspidant Sieb. et Zucc., Aloe ferox Miller and Rumex japonicus Houtt. decoction
Table 4. Comparison of contents (moL) of polyphenols in the decoction of three herbs before and after acid hydrolysis