Color and molecular structure alterations of brazilein extracted from Caesalpinia sappan L. under different pH and heating conditions

Abstract

Brazilein extract from sappan wood (Caesalpinia sappan L.) has potential for use as natural food colorant since it has no unique flavor and taste. Although brazilein has long been applied in several traditional foods and beverages, information on its stability, which is of importance for practical application, is still limited. In this work, brazilein was isolated from sappan wood; its purity was confirmed by nuclear magnetic resonance spectroscopy. Relations between molecular structures and color as well as thermal stabilities of brazilein in aqueous solutions at pH 3, 7 and 9 were for the first time investigated. At the lowest pH, zero net-charge structure of brazilein, which exhibited yellow color, was predominantly found. The deprotonated and fully deprotonated structures of brazilein, which exhibited orange and red colors, respectively, were found when pH of the aqueous solutions increased. The forms of brazilein existing at the higher pH suffered extensive degradation upon heating, while the form existing at the lowest pH possessed higher stability. Heat-induced deprotonation and degradation were confirmed by UV-visible and Fourier-transform infrared spectra as well as losses of brazilein content. Sappan (Caesalpinia sappan L.), which has several such local names as Buckham wood in English, Bois de sappan in French, Pau de sappan in Polish, Sappanholz in German, Su mu in Chinese, Suo in Japanese and Fang in Thai, is a wood in the family Leguminosae. This wood is naturally available throughout Asia, including China, Japan and Thailand. Due to its several valuable functions, this wood plant is also nowadays cultivated in various other regions of the world, including Africa, Europe as well as North and South Americas. Dried heartwood of sappan has long been used as herbal medicines as it contains many phytochemicals and bioactive compounds 1-5. The biological abilities of the wood extract in terms of antiacne 6 , anti-bacterial 7,8 , anticancer 9 , antidiabetic 10 , antidiarrhea 11 , antiinflammatory 12-14 , antioxidant 15 and anti-photoaging 16 activities have been demonstrated by a number of researchers. The major active ingredient of sappan is brazilin, which is a colorless phenolic compound consisting of two aromatic rings, one pyrone and one five-membered ring. Based on its molecular structure, brazilin is identified as a neoflavonoid. However, hydroxyl group in the brazilin structure is easily oxidized and can change into carbonyl group, resulting in the structural transformation and formation of brazilein, which is a colored compound 17-19. Brazilein has indeed widely been used as a natural colorant; sappan extract containing brazilein has traditionally been used in the painting of books as well as in the dyeing of silk and wool. Since an aqueous extract of sappan possesses many beneficial properties over other red-color pigments, e.g.

Enhancement of The Sappanwood Extract Yield by Aqueous Ultrasound-Assisted Extraction Using Water Solvent

“…On the other hand, when the extraction process was delayed, the part of brazilin was oxidized. Thus, brazilein content increases appreciably [7].…”

“…Depending on the pH, brazilin appears to be amber to red in color, where the red color can be obtained under basic conditions (pH >7) [7]. Exposure to light, pH, and air may induce the oxidation of brazilin to form brazilein due to the alteration of a hydroxyl group to the carbonyl group, which is responsible for the intense red color of the sappanwood extract [7], [8].…”

“…Depending on the pH, brazilin appears to be amber to red in color, where the red color can be obtained under basic conditions (pH >7) [7]. Exposure to light, pH, and air may induce the oxidation of brazilin to form brazilein due to the alteration of a hydroxyl group to the carbonyl group, which is responsible for the intense red color of the sappanwood extract [7], [8]. Based on his study on the storage of sappanwood water extract at 4°C and 25°C under neutral and basic conditions (pH 7.0, 8.0, and 9.0), Sinsawasdi confirmed that the exposure to light at a given pH gave a more pronounced brazilin degradation to Brazilian that the exposure to higher temperature [9].…”

“…The previous research about brazilin extraction from sappanwood studied the brazilin yield [1], [15] and its pharmacological properties [1], [7]. The process transfer during the extraction involving diffusion of brazilin to solvent and extraction rate were scared.…”

Development of Eco-friendly Dyeing Process Based on Caesalpinia sappan L. Bark, Cocos nucifera Fiber and Leucaena leucocephala Leaves

“…Sappanwood extracts in addition to functioning as a natural red dye, also show great benefits as antibacterial agents [38], [40]- [42], antioxidants [38], [43]- [45], and pharmacological activity [46]. Also, braziline is easily oxidized by light to form a very red brazilein [35], [38]. Characterization with UV-Vis spectroscopy and μ-spectrofluorimetry revealed that in its acid form, brazilein chromophores provide maximum absorption, excitation, and emission respectively at wavelengths of 446, 475 and 536 nm and 540, 548 and 560 nm when deprotonated.…”