FT-NIRS Coupled with PLS Regression as a Complement to HPLC Routine Analysis of Caffeine in Tea Samples

Daily consumption of caffeine in coffee, tea, chocolate, cocoa, and soft drinks has gained wide and plentiful public and scientific attention over the past few decades. The concentration of caffeine in vivo is a crucial indicator of some disorders—for example, kidney malfunction, heart disease, increase of blood pressure and alertness—and can cause some severe diseases including type 2 diabetes mellitus (DM), stroke risk, liver disease, and some cancers. In the present study, near-infrared spectroscopy (NIRS) coupled with partial least-squares regression (PLSR) was proposed as an alternative method for the quantification of caffeine in 25 commercially available tea samples consumed in Oman. This method is a fast, complementary technique to wet chemistry procedures as well as to high-performance liquid chromatography (HPLC) methods for the quantitative analysis of caffeine in tea samples because it is reagent-less and needs little or no pre-treatment of samples. In the current study, the partial least-squares (PLS) algorithm was built by using the near-infrared NIR spectra of caffeine standards prepared in tea samples scanned by a Frontier NIR spectrophotometer (L1280034) by PerkinElmer. Spectra were collected in the absorption mode in the wavenumber range of 10,000–4000 cm−1, using a 0.2 mm path length and CaF2 sealed cells with a resolution of 2 cm−1. The NIR results for the contents of caffeine in tea samples were also compared with results obtained by HPLC analysis. Both techniques provided good results for predicting the caffeine contents in commercially available tea samples. The results of the proposed study show that the suggested FT-NIRS coupled with PLS regression algorithun has a high potential to be routinely used for the quick and reproducible analysis of caffeine contents in tea samples. For the NIR method, the limit of quantification (LOQ) was estimated as 10 times the error of calibration (root mean square error of calibration (RMSECV)) of the model; thus, RMSEC was calculated as 0.03 ppm and the LOQ as 0.3 ppm

Chemical, molecular and structural studies of Boswellia species: β-Boswellic Aldehyde and 3-epi-11β-Dihydroxy BA as precursors in biosynthesis of boswellic acids.

The distribution and biosynthesis of boswellic acids (BAs) is scarce in current literature. Present study aims to elucidate the BAs biosynthetic and its diversity in the resins of Boswellia sacra and Boswellia papyrifera. Results revealed the isolation of new (3β, 11β-dihydroxy BA) and recently known (as new source, β-boswellic aldehyde) precursors from B. sacra resin along with α-amyrin. Following this, a detailed nomenclature of BAs was elucidated. The quantification and distribution of amyrins (3-epi-α-amyrin, β-amyrin and α-amyrin) and BAs in different Boswellia resins showed highest amyrin and BAs in B. sacra as compared with B. serrata and B. papyrifera. Distribution of BAs significantly varied in the resin of B. sacra collected from dry mountains than coastal trees. In B. sacra, high content of α-amyrin was found in the roots but it lacked β-amyrin and BAs. The leaf part showed traces of β-ABA and AKBA but was deficient in amyrins. This was further confirmed by lack of transcript accumulation of amyrin-related biosynthesis gene in leaf part. In contrast, the stem showed presence of all six BAs which are attributed to existence of resin-secretory canals. In conclusion, the boswellic acids are genus-specific chemical constituents for Boswellia species albeit the variation of the amounts among different Boswellia species and grades

Quantification of amyrins and BAs in different <i>Boswellia</i> tree parts.

<p>Quantification of amyrins and BAs in different <i>Boswellia</i> tree parts.</p

Configuration of amyrins and boswellic acids.

<p>Configuration of amyrins and boswellic acids.</p

Resin extraction from <i>B</i>. <i>sacra</i> tree.

<p>a) <i>B</i>. <i>sacra</i> tree, Dhofar, Oman, b) milky substance is oozing out after the first incision, c) frankincense after a few days of incision, d) the final product of frankincense. All photos are from the authors’ lab.</p

Formation of boswellic acid derivatives.

<p>Formation of boswellic acid derivatives.</p

Conversions of α-amyrin and β-amyrin into boswellic acids.

<p>Conversions of α-amyrin and β-amyrin into boswellic acids.</p

Transversal and radial sectioning of <i>B</i>. <i>sacra</i> stem part structure and analysis through Scanning Electron Micrographs.

<p>The micrographs are representative to ten individual stem parts of the tree. The Micrographs are taken on SEM using 50 to 200 μM section and zoom from 100x to 1.2Kx. SC = Sclerenchyma; PC = Parenchyma; AC = Axial canals; RRC = Radial resin canal; IB = Inner bark; OB = Outer bark.</p

RT-PCR analysis of α<i>-amyrin synthase</i> (AS) and <i>Squalene-synthase</i> (SS) in the leaf part of <i>B</i>. <i>sacra</i>.

<p>The values are mean of three replications and bars with * shows values are significantly (P<0.05) different from the expression of Actin.</p

Formation of pentacyclic isomers.

<p>Formation of pentacyclic isomers.</p