Application of chemometrics in quality control of Turmeric (Curcuma longa) based on Ultra-violet, Fourier transform-infrared and ¹H NMR spectroscopy

Highlights

• Metabolic profiling of Turmeric by UV, FT-IR and ¹H NMR in comparison to HPLC.

• PCA and HCA were applied to discriminate high quality samples from low quality ones.

• UV discriminated between samples, as simple fast technique alternative to HPLC.

• Metabolic variability was evident in essential oils/fatty acid region in ¹H NMR.

• First time to apply UV, FT-IR and ¹H NMR for the quality control of Turmeric.

Abstract

Turmeric (Curcuma longa L.) belongs to the family Zingiberaceae that is widely used as a spice in food preparations in addition to its biological activities. UV, FT-IR, ¹H NMR in addition to HPLC were applied to construct a metabolic fingerprint for Turmeric in an attempt to assess its quality. 30 samples were analyzed, and then principal component analysis (PCA) and hierarchical clustering analysis (HCA) were utilized to assess the differences and similarities between collected samples. PCA score plot based on both HPLC and UV spectroscopy showed the same discriminatory pattern, where the samples were segregated into four main groups depending on their total curcuminoids content. The results revealed that UV could be utilized as a simple and rapid alternative for HPLC. However, FT-IR failed to discriminate between the same species. By applying ¹H NMR, the metabolic variability between samples was more evident in the essential oils/fatty acid region.

Introduction

Herbal medicine plays an important role in health care systems worldwide. The standardization and quality control of these herbal products are a major problem that limits their integration in the western medicine. Over the last few decades, more steps were taken not only to improve and advance the quality of the herbal products but also to develop suitable and reliable analytical methods confirming their quality. Nowadays, the uses of different chromatographic and spectroscopic fingerprinting are the most acknowledged techniques in the assessment and quality control of many herbal products in combination with chemometrics (Gad, El-Ahmady, Abou-Shoer, & Al-Azizi, 2012).

Turmeric (Curcuma longa L.) belongs to the family Zingiberaceae, is a perennial rhizomatous shrub native to Southern Asia. Today, the species cultivation has also widely distributed to some African countries. “Curcuminoids”, the principal natural yellow pigments comprising curcumin, demethoxycurcumin and bisdemethoxycurcumin Fig. 1, are the main chemical components related to the bioactivities of Turmeric (Jayaprakasha, Jagan Mohan.Rao, & Sakariah, 2002). These three curcuminoids have been proved to show strong anti-oxidant (Ak & Gülçin, 2008), anti-inflammatory (Jurenka, 2009), anti-bacterial (Gunes et al., 2016, Sasidharan et al., 2014), anti-viral, anti-fungal (Moghadamtousi et al., 2014), anti-carcinogenic (Parsai et al., 2014, Rahmani et al., 2014), anti-epileptic (Noor, Aboul Ezz, Faraag, & Khadrawy, 2012), immune-stimulatory (Yue et al., 2010), anti-depressant (Bhutani, Bishnoi, & Kulkarni, 2009), nephroprotective and hepatoprotective activities (Osawa, 2007, Rivera-Espinoza and Muriel, 2009) as well as neuroprotective activities (Tizabi, Hurley, Qualls, & Akinfiresoye, 2014).

In addition to its biological activities, Curcuma longa is known as the ‘golden spice of life’ as it is widely used for its flavoring, as a spice in food preparations; it retains the nutritional value of different food items due to its specific flavor and color (Ravindran, Nirmal Babu, & Sivaraman, 2007). Turmeric is a main component in curry powders and pastes. In the food industry, it is commonly utilized in soups, sauces, and in a variety of other products as coloring and flavoring agent. Recently, the powder has also been used as a colorant in cereals. The food industry and enforcement authorities necessitate authenticated methods for the analysis of curcumin (Scotter, 2009).

Both qualitative and quantitative analyses have been recognized as a significant approach in the quality control of herbal medicines either in their raw form or in final products. Various methods have been detected for the quality control of Turmeric via the quantification of the total curcuminoids content; these include HPTLC (Paramasivam et al., 2009, Zhang et al., 2008), HPLC (Singh et al., 2010, Syed et al., 2015), UPLC (Cheng et al., 2010) and capillary electrophoresis (CE) (Anubala et al., 2014, Lechtenberg et al., 2004). In addition, HPLC combined with mass spectroscopy was developed for the simultaneous analysis of three curcuminoids in the crude extract of Curcuma longa (Li et al., 2011; W. Li, Xiao, Wang, & Liang, 2009). Furthermore, comparison of conventional HPLC method with UPLC was carried out for quantification of three curcuminoids (Cheng et al., 2010). LC–MS/MS was developed for simultaneous identification and quantification of three curcuminoids in Curcuma wenyujin (Jiang et al., 2006, Shen et al., 2013). However, HPLC is the most applied method, as it is known for its effectiveness and rapid separation.

Additionally, GC–MS was used to assess its quality and to discriminate between different ecotypes of Curcuma (C. wenyujin, C. kwangsiensis and C. phaeocaulis) (Xiang, Wang, Cai, & Zeng, 2011). FT-IR combined with PCA and CVA for the identification and discrimination of Curcuma longa, Curcuma xanthorrhiza and Zingiber cassumunar. Discrimination of the three species was achieved by both PCA and CVA, in which CVA gave clearer discrimination (Rohaeti, Rafi, Syafitri, & Heryanto, 2015).

Alternative techniques such as UV, FT-IR and ¹H NMR are to be explored to assess the quality control of Turmeric, as they are fast, simple and require minimal sample preparations in comparison to traditional methods of analysis as HPLC.

Therefore, the aim of this study is to find out other analytical techniques rather than HPLC for the quality control of Curcuma longa. UV, FT-IR and ¹H NMR were utilized in this study as powerful spectroscopic techniques as they are previously applied for the quality control of different herbal medicines (Gad et al., 2013, Kuhnen et al., 2010, Rohman and Man, 2010, Roshan et al., 2013, Sârbu et al., 2012, Yang et al., 2012, Yap et al., 2007). Complete metabolic profiles were established by UV, FT-IR and ¹H NMR, the obtained results were compared to the data obtained from HPLC. Classification of samples was achieved by applying Principal Component Analysis (PCA) and Hierarchal Cluster Analysis (HCA) on the data generated from different techniques to find out the most powerful technique to obtain a phytochemical profile to assess the quality of Curcuma and to segregate high-quality samples from low quality ones. To our knowledge, it is the first time to apply UV, FT-IR and ¹H NMR for the quality control of Curcuma longa.