Quality Control of Herbal Medicines with Spectrophotometry and Chemometric Techniques – Application to Baccharis L. Species Belonging to Sect – Caulopterae DC. (Asteraceae)

Medicinal plants constitute a rich cultural and biological heritage in many countries, which could be very useful in meeting the therapeutic needs of the population (Rodriguez, 2010a). Traditional herbal medicines have been widely used for many years in many eastern countries (Liang et al., 2004). However, little work has been done to validate and standardize these products properly in order to match phytotherapy to chemotherapy which currently receives almost unconditional support from formal systems of health care. For several years now activities have been undertaken to systematize the identification, validation, production and use of medicinal plants, for both primary health care as well as a semi-industrial or industrial process, which implies their transformation into safe, reliable and stable phytopharmaceutical products. Therefore it is suggested that medicinal plants and their derived products would be a viable option for national development as an agricultural and therapeutic alternative, but standardization and industrialization, involving sustained yields, a quality control system and honest and reliable marketing would be needed for widespread implementation and official support. Consequently, on account of the above, education and research should be in agreement if any advance is to be made in this area (Rodriguez, 2010a). However, the necessary criteria for data quality, safety and efficacy of traditional medicine that would support its use in the world do not exist. Appropriate, accepted research methodology for evaluating traditional medicine is also lacking (Liang et al., 2004).


Introduction
Medicinal plants constitute a rich cultural and biological heritage in many countries, which could be very useful in meeting the therapeutic needs of the population (Rodriguez, 2010a). Traditional herbal medicines have been widely used for many years in many eastern countries (Liang et al., 2004). However, little work has been done to validate and standardize these products properly in order to match phytotherapy to chemotherapy which currently receives almost unconditional support from formal systems of health care. For several years now activities have been undertaken to systematize the identification, validation, production and use of medicinal plants, for both primary health care as well as a semi-industrial or industrial process, which implies their transformation into safe, reliable and stable phytopharmaceutical products. Therefore it is suggested that medicinal plants and their derived products would be a viable option for national development as an agricultural and therapeutic alternative, but standardization and industrialization, involving sustained yields, a quality control system and honest and reliable marketing would be needed for widespread implementation and official support. Consequently, on account of the above, education and research should be in agreement if any advance is to be made in this area (Rodriguez, 2010a). However, the necessary criteria for data quality, safety and efficacy of traditional medicine that would support its use in the world do not exist. Appropriate, accepted research methodology for evaluating traditional medicine is also lacking (Liang et al., 2004).
testing and specifications of identity, purity and contents of the principal active ingredients or markers for each plant drug, in order to guarantee the conservation of the species and the specifications of microbiological purity. Currently the quality requisites of the different national pharmacopoeias vary between countries, however the International Federation of Pharmaceutical Manufacturer Associations, have taken a first step towards the global implementation of organized criteria (International Federation of Pharmaceutical Manufacturer Associations [IFPMA], 1997). The World Health Organization has conducted a review of the legal status of traditional medicine and complementary or "alternative" therapies in 123 countries (World Health Organization [WHO], 2001). Moreover, some countries and organizations have developed, or are developing, their own monographs, for example, the Commission E of the German Ministry of Health, WHO and European Scientific Cooperative on Phytotherapy, China, Brazil and Argentina, among others. These monographs recognise the quality standards applicable to drugs and herbal remedies in the pharmaceutical market. (Blumenthal, 1998; European Scientific Cooperative on Phytotherapy [ESCOP], 2003;Keller, 1991;WHO, 1991WHO, , 1999WHO, , 2002. In Argentina there is great interest in controlling the Quality, Security and Efficacy of herbal medicines. In order to achieve this ambitious objective the following steps must be taken: a-Registration of the products, b-Verification of good practices of production and quality control, of the crude drug and its products, and c-Pharmacovigilance. ANMAT (National Administration of Drug, Food and Medical Technology) is the organism responsible for authorizing all activities related to medicines through its technical organism, the INAME (National Institute of Drug). The products based on herbal medicine and aromatics are considered as Phytotherapeutic Drugs in Resolution Nº 144/98 and the Supplementary Provisions (Provision 2671/99; Provision 2672/99; Provision 2673/99) that are now in effect. Provision 1788/2000 contains a list of 109 herbal medicines that can not be authorised for the production of herbal medicine on account of the contradictions or toxic effects reported in their traditional use.
It is very important that plant material is of the highest quality as it is used as a medicine. The aforementioned decrees aim to guarantee the quality of the raw material, the intermediate and finished products and a series of tests have been established among which, as a minimum requisite, are botanical identity, purity (physical-organoleptic and microbiological -for health) and their activity or composition (methodological analysis), taking into account the Good Practices of Agricultural Production and the Good Practices of Manufacturing (Rodriguez, 2010a).

Spectrophotometry and chemical fingerprints of herbal medicines
In general one or two markers or pharmacologically active compounds of herbal components or herbal blends were used to evaluate the quality and authenticity of herbal medicines in the identification of a single herb or preparation of herbal medicine and to evaluate the quantitative composition of a herbal product. However, this type of determination does not give a complete picture of the herbal products because multiple ingredients are usually responsible for its therapeutic effects. These therapeutic effects may work synergistically and change their activity on being separated into their active parts. So various analytical techniques can be applied for this type of registration and the complete herbal product can be considered as the "active compound" (Liang et al., 2004).

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The concept of phytoequivalence was developed in Germany to ensure the consistency of herbal products (Tyler, 1999). According to this concept, a chemical profile, such as a spectrophotometric fingerprint for a herbal product should be constructed and compared with the profile of a clinically tested reference product. Therefore, a spectrophotometric fingerprint of a herbal medicine is a spectrophotometric pattern of an extract of some chemical components that are pharmalogically active and/or with chemical characteristics. I t i s s u g g e s t e d t h a t w i t h t h e h e l p o f s p ectrophotometric fingerprints obtained, the authentication and identification of herbal medicines would be appropriate, even when the amount and/or concentration of some typical chemical ingredients are not exactly the same for different samples of these herbal medicines. In this way, we are broadly considering multiple ingredients in the extracts of herbal medicines rather than one or two marker ingredients for evaluating the quality of the herbal products.
In general various analytical techniques can be used to obtain fingerprints of herbal medicines of which chromatography is most often used on account of its great efficiency in separating the different components of an extract. For the above mentioned reasons these chromatographic techniques have a high cost, especially if they are to be used for routine quality control. A simple alternative technique such as UV/Visible spectrophotometry, coupled to chemometric methods was carried out by Lonni et al. (2005) for taxonomic purposes. Authors were able to separate populations of three species of Baccharis according to their UV / Visible spectra. Here, we propose to apply the same methodology as part of quality control of herbal medicines. Figure 1 shows the spectrophotometric profiles of ethanol extracts of the aerial parts of Baccharis gaudichaudiana DC. obtained from five areas in Misiones province, Argentina (MI1, MI2, MI3, MI4, MI5) (Rodriguez, 2010b). Here, of course, some differences can be observed in the profiles; however phytoequivalence for B. gaudichaudiana can be seen.

Chemometric methods and quality control
The chemometric methods consist of a number of statistical, mathematical and graphic techniques that analyze many variables simultaneously (Lonni, 2005). The method used in this study is as follows: Principal components analysis (PCA).
This method is based on the transformation of a group of original quatitative variables into another group of unrelated independent variables, known as principal components. The components have to be interpreted independently of one another, as they contain part of the variance that is not expressed in any other principal component (Pla, 1986;López & Hidalgo, 1994).
The criterion of Cliff in 1987 was adopted for selecting the number of components that should be used for the analysis, which states that the eigenvalues of acceptable components should explain 70% of the total variance (López & Hidalgo, 1994).
Proportion of variance explained: in general statistical programs provide information of the eigenvectors and, in some cases, the correlation between the original variables and the principal components. However, these correlations can be calculated from the eigenvectors in the following formula (Pla, 1986): where, r(jk)= correlation between the original variable x(j) and the k-esim component.

s(ij) = variances of the correlation matrix.
In most studies it is important to determine the degree of discrimination of the variables so that those with the most and least variation can be identified.
Using PCA it is possible to determine the degree of discrimination, quantifying the proportion of variance explained by each original variable of the selected components; to do this it is necessary to add the squares of the correlation formed by each original variable with the selected components. This is possible as the components are not correlated (Pla, 1986). In the case of a variable in series: rx12 + rx22 + rx32 = proportion of the variance explained, having selected three components. It should to be taken into account that the variables that explain a larger proportion of variance are the most discrimatory and therefore they are more important.
The UV/Visible spectra of populations of two species, Baccharis articulata (Lam.) Pers. and B. trimera can be seen in Figure 2. In this figure it is difficult to distinguish which spectrum corresponds to which species, but the resolution is greater when PCA is applied ( Figure 3) and different coordinates can be seen for the corresponding populations of one species or another. authors have contributed to the infrageneric classification of Baccharis in general and regional floras (Ariza Espinar, 1973;Baker, 1882Baker, -1884Barroso, 1976;Cuatrecasas, 1967;De Candolle, 1836;Giuliano, 2001;Heering, 1904;Lessing, 1831;Weddell, 1855Weddell, -1856 and it was De Candolle (1836) who was the first to subdivide the genus in eight sections, mainly based on leaf morphology. More recently, Giuliano (2001) grouped 96 Argentine Baccharis species into 15 sections, among which the sect. Caulopterae DC. is characterized by the presence of species with alate stems. Two of nine Argentine species from this sect., i.e., Baccharis articulata (Lam.) Pers. and Baccharis crispa Spreng. are included in the National Argentine Pharmacopeia Ed. VI (1978), and a third one, Baccharis trimera (Less.) DC. in the Brazilian Pharmacopeia Ed. IV (2002) with the common name of "Carquejas". The nine species of this sect. are traditionally used in infusions or decoctions, as hepatic, colagogue, diuretic, ulcer healing and external antiseptics. They are also used in herbal remedies and phytotherapy and in the preparation of spirits and soft drinks (Correa, 1985;Gupta, 1995;Hieronymus, 1882;Martínez Crovetto, 1981;Sorarú & Bandoni, 1978;Toursarkissian, 1980). Beneficial effects of these species can be attributed in part to their high content of flavonoids. The chemistry of the flavonoids is predictive of their free radical scavenging activity, which confers the antioxidant activity (Harborne & Williams, 1992;Rice-Evans et al., 1995).
Currently, the morphoanatomical studies of these species in sect. Caulopterae only provide incomplete information which makes it difficult to differentiate each one properly in the non-flowering condition when the size of capitulum of each one varies (Giuliano, 2000;Müller, 2006). This fact has lead to the misuse of the same common name for botanically diverse species, which surely have different chemical compositions and therefore different pharmacological properties (Abdel-Malek et al., 1996;Desmarchelier et al., 1997 Gene et al., 1992Gene et al., , 1996Lapa et al., 1992;Palacios et al., 1983;Stoicke & Leng-Peschlow, 1987). Also the high frequency of errors committed during the collection of these species for medicinal purposes is understandable due to the coexistence of these entities in certain habitats. Hence, considering that numerical methods have been shown to be useful for multi-component metabolic classification studies, we decided to carry out population studies including 53 samples of these nine sect. Caulopterae species, combining their spectrophotometric profiles with multivariate analysis. These nine species belonging to sect. Of these nine species, only three are official and its use is permitted but all are indiscriminately collected for medicinal purposes due to their similar morphotypes as they have alate stem.

Material and methods
Fifty three samples of nine Baccharis species were collected from wild materials in different locations in Argentina. All samples were botanically identified by our group and voucher specimens were deposited at the herbarium of the National University of Rosario, Argentina (Table 1).
The aerial parts of the dried plants (5 g) were macerated (24 h, 3x) with absolute ethyl alcohol. The ethanolic extract was filtered and concentrated in a rotary evaporator at a temperature lower than 100 ºC. Thirty mg of dry extract were mix in 3 ml dichloromethane (DCM) and left for 1 h and then filtered with common filter paper. A dilution of 50 µl of this solution in 950 µl of methanol was prepared and filtered twice with a 0.45 µm Millipore filter (Lonni et al., 2003(Lonni et al., , 2005.
Spectrophotometric analyses were carried out using a Biochrom Model Libra S12 UV/Visible Spectrophotometer, equipped with tungsten halogen and deuterium arc light sources with a single solid state silicon photodiode detector, and operating software.
HPLC analyses were carried out using a Spectra Physics Model SP8800 ternary pump chromatograph with Spectra 100 UV/Visible detector, having as chromatographic conditions, methanol eluent, 1 ml min -1 flow, Luna C18 phenomenex (250 x 4.6 mm, 5 µm particle size). The injection volume was 100 µl and elution was monitored al 254 nm. Apigenin, genkwanin and luteolin were used as markers (purchased from Extrasynthèse, France).
TLC and HPLC analysis were applied in order to complement the studies carried out by PCA of the spectrophotometric data and to find potential markers of the species that could not be characterized by the previous method. Numbers indicate when there is more than one population of the same species. a Material extracted from Herbarium; b Names of collectors, numbers not provided by the Herbarium.

Statistical analysis
Principal components analysis (PCA) was applied to the population study. The analysis was performed using the NTSYS-pc 2.11w (Numerical Taxonomy and Multivariate Analysis System) designed by Rohlf (1998).
Basic data matrix was prepared considering 700 absorbance values (quantitative variable) of each analysed sample (53 extracts in total).

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Quality Control of Herbal Medicines with Spectrophotometry and Chemometric Techniques -Application to Baccharis L. Species Belonging to Sect -Caulopterae DC. (Asteraceae)

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Before PCA the data were pre-processed with normalization to unit area technique (Beebe et al., 1998).

Spectrophotometric analysis
Seven hundred absorbance values were utilised as quantitative variables for population analysis. Samples were collected in different provinces and seasons, mainly taking into account the quantitative variability of secondary metabolites during the year (Table 1). The principal component analysis showed that the first nine components explain almost 98.81% of the total variability. The second (PC2) and the third (PC3) principal components gathered relevant information for classifying species. Figure 4,  Spectrophotometric PCA data allowed the distinction of six out of the nine species examined in this study. However the three species B. articulata, B. gaudichaudiana and B. sagittalis could not be separated which is shown in the figure 6, where it is seen that the average spectra of the species are very similar.
As can be observed in Figure 4,     B. penningtonii species samples have negative PC9 scores; PC9 separates B. penningtonii samples from the rest as seen in Figure 5. Figure 8 A shows a graph of the loading values (eigenvalues) on PC9 vs. ; it also shows that two regions present negative values between: 200 and 250 and 320 and 370 nm and it can be observed that the most intense analytical signals for B. penningtonii species samples are in these regions (Figure 8 B). These results suggest that the substances responsible for the discrimination between species are those which have peaks around 225, 250, 300, 325, 350, 375 and 425 nm. Considering that the ethanol extracts used in this study might possess mainly flavonoids and that the region studied is where they present their main absorption bands (Greenham et al., 2003), it is likely that the components responsible for the spectra in this work would be flavonoids. It is worth taking into account that previous studies on the phytochemistry of Baccharis spp. have shown the presence of flavonoids, mainly flavanones and flavones (Coelho et al., 2004;Gene et al., 1996;Torres et al., 2000). From species of this genus 298 flavonoids were isolated. Among them 24 were flavanones and 85 were flavones and among them 48% are oxygenated in the C-3 (Gonzaga Verdi et al., 2005). They were described as good chemotaxonomic markers for the lower hierarchical levels of the Asteraceae family (Emerciano et al., 2001). In contrast to other characterization studies in which it is necessary to isolate and identify chemical substances, this study uses the complete ultraviolet-visible spectra measured between 200 nm to 900 nm, avoiding the isolation, purification and characterization of chemical compounds (Lonni et al., 2005). This methodology does not distinguish the spectra of individual components in the extract. Instead, the full spectrum ranges are analyzed as a whole. Absorption spectra of figure 7 C show that the qualitative composition of flavonoids is different in the different species.
It has previously been observed that there is variability in the contents of several compounds in the different Baccharis species (Dresch et al., 2006;Gonzaga Verdi et al., 2005). With regards to the seasons, Borella et al. (2001) observed variations in the content of the total flavonoids, the largest number being found in a drug in the summer, which is an expected result due to the large number of functions attributed to them (Harborne & Williams, 2000). Our results are consistent with previous ones, showing different heights of peaks in the spectra in Figure 6, 7C and 8 B, even though these spectra were standardized. In a fertilization trial of B. trimera, in which the nutrient content of the soil was varied, no variation was observed in the contents of flavonoids (Borella et al., 2001). In our study we observed some changes in the content of flavonoids between collecting regions (Figure 4 and 5) but these did not prevent the grouping of various populations of the same species.
A routine step in multivariate data analysis is ordinarily to obtain a low-dimensional representation of the data. If two or three main components gives an accurate representation, a bi-or three-dimensional graph could be realized which mere observation is instructive. Clusters are usually easy to detect. After analysis of the eigenvalues (PC loading), more discriminant original variables are obtained. Then an ANOVA must be performing of each of these original variables between the OTUS (here species). The higher the eigenvalues, regardless of the sign will be more efficient in discriminating the OTUS. Variables that have negative eigenvalues (-) means that they are characterizing in the opposite direction in relation to the variables that have positive eigenvalues (+) and vice versa.
Thus, absorbance values of the wavelengths (225, 250, 300, 325, 350, 375 and 425 nm) obtained from the analysis of the eigenvalues were submitted to ANOVA and we have established the wavelengths that differ between pairs of species (

TLC analysis
A TLC analysis was initiated of the dichloromethane extracts of B. articulata, B. gaudichaudiana and B. sagittalis used to perform UV-Visible spectra using the mobile phase DCM: Hexane: MeOH (4:2:1) in order to complement the studies carried out by PCA of the spectrophotometric data and to find potential markers of the species that could not be

Conclusion
The growing tendency to use high quality, standardized plant extracts, with a guarantee of security and efficacy, is going to continue. Therefore, all efforts should be directed at researching the chemical-pharmalogical profiles of the extracts and combinations and in rationalizing their therapeutic applications.
In the present example, sect. Caulopterae species are very similar between them and only B. articulata, B. crispa and B. trimera are official in pharmacopeia. UV/Visible spectrophotometry coupled to PCA grouped populations of these three species in different areas in a two dimensional graph. Three additional species were grouped in different areas in the same graph too (B. microcephala, B. phyteumoides and B. penningtonii). Populations of species that fall outside the areas of official species are unfit for medicinal purposes. It should be noted that in the case of the official species B. articulata, additional techniques, such as TLC should be applied to distinguish between B. articulata, B. gaudichaudiana and B. sagittalis. According to this, the combination of these techniques could to be used for routine quality control of official herbal medicines.

Acknowledgment
The present work was supported by a grant from the Agencia Nacional de Promoción Científica y Vol 2, Ginebra.