Kit L. Chin

Phytochemistry, antioxidant capacity, total phenolic content and anti-inflammatory activity of Hibiscus sabdariffa leaves

A liquid chromatography-mass spectrometry method was developed for the simultaneous separation, and determination of natural compounds including phenolic acids and flavonoids in the leaves of Hibiscus sabdariffa. By analyzing the UV and MS data, and comparison with authenticated standards, 10 polyphenols including neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid, quercetin, kaempferol and their glycosides were identified together with 5-(hydroxymethyl)furfural. Major constituents in the leaves of 25 different populations from worldwide accessions were quantified and compared with each other. The total phenolic content of each accession was determined using Folin-Ciocalteu assay, ranging from 18.98 ± 2.7 to 29.9 ± 0.5 mg GAE/g. Their in vitro antioxidant activities were measured by ABTS radical cation decolorization assay, varying from 17.5 to 152.5 ± 18.8 μmol Trolox/g. After the treatment of H. sabdariffa leaf extract, the reduction of LPS-induced NO production dose-dependently in RAW 264.7 cell indicates the extracts potential anti-inflammatory activity.

Antioxidant Activity of Leaf Extracts from Different Hibiscus sabdariffa Accessions and Simultaneous Determination Five Major Antioxidant Compounds by LC-Q-TOF-MS

Hibiscus sabdariffa has gained attention for its antioxidant activity. There are many accessions of H. sabdariffa in the world. However, information on the quantification of antioxidant compounds in different accessions is rather limited. In this paper, a liquid chromatography/quadrupole-time-of-flight mass spectrometry (LC-Q-TOF-MS) method for simultaneous determination of five antioxidant compounds (neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid, rutin, and isoquercitrin) in H. sabdariffa leaves was developed. The method was validated for linearity, sensitivity, precision, repeatability and accuracy. The validated method has been successfully applied for determination of the five analytes in eight accessions of H. sabdariffa. The eight accessions of H. sabdariffa were evaluated for their antioxidant activities by DPPH free radical scavenging assay. The investigated accessions of H. sabdariffa were rich in rutin and exhibited strong antioxidant activity. The two accessions showing the highest antioxidant activities were from Cuba (No. 2) and Taiwan (No. 5). The results indicated that H. sabdariffa leaves could be considered as a potential antioxidant source for the food industry. The developed LC-Q-TOF-MS method is helpful for quality control of H. sabdariffa.

Variations in chemical fingerprints and major flavonoid contents from the leaves of thirty-one accessions of Hibiscus sabdariffa L.

Abstract The leaves of Hibiscus sabdariffa L. have been used as traditional folk medicines for treating high blood pressure and fever. There are many accessions of H. sabdariffa L. throughout the world. To assess the chemical variations of 31 different accessions of H. sabdariffa L., fingerprinting analysis and quantitation of major flavonoids were performed by high‐performance liquid chromatography (HPLC). The HPLC method was validated for linearity, sensitivity, precision, repeatability and accuracy. A quadrupole‐time‐of‐flight mass spectrometry (Q‐TOF‐MS) was applied for the characterization of major compounds. A total of 9 compounds were identified, including 6 flavonoids and 3 phenolic acids. In the fingerprint analysis, similarity analysis (SA) and principal component analysis (PCA) were used to differentiate the 31 accessions of H. sabdariffa L. Based on the results of PCA and SA, the samples No. 15 and 19 appeared much different from the main group. The total content of five flavonoids varied greatly among different accessions, ranging from 3.35 to 23.30 mg/g. Rutin was found to be the dominant compound and the content of rutin could contribute to chemical variations among different accessions. This study was helpful to understand the chemical variations between different accessions of H. sabdariffa L., which could be used for quality control.

High-Performance Thin-Layer Chromatographic Method for Screening Antioxidant Compounds and Discrimination of Hibiscus sabdariffa L. by Principal Component Analysis

The leaves of Hibiscus sabdariffa L. are one of the sources of food and traditional medicine. A combination of high-performance thin-layer chromatography (HPTLC) bioautographic assay with mass spectrometry (MS) has been performed to screen and identify the antioxidant compounds in the leaves of H. sabdariffa L. The crude extract of H. sabdariffa L. was separated on silica gel 60 HPTLC plates in an automatic developing chamber (ADC2) with toluene-ethyl acetate-formic acid-methanol (6:6:1.6:1, v/v) as the mobile phase. Antioxidant bands were visualized by dipping in 2,2-diphenyl-1-picrylhydrazyl (DPPH) reagent. Five antioxidant compounds were identified as neochlorogenic acid (1), chlorogenic acid (2), cryptochlorogenic acid (3), rutin (4), and isoquercitrin (5), which could be the predominant contributors to the antioxidant activity of the leaves of H. sabdariffa L. Furthermore, principal component analysis (PCA) was carried out to discriminate ten accessions of H. sabdariffa L. using an image-processing software. This simple HPTLC fingerprint assisted by PCA can be used as a reliable method for the discrimination of different accessions of H. sabdariffa L.

Localization of UV Absorbing Compounds in Nuttall Oak (Quercus nuttallii) Leaves Using Naturstoffreagenz-A (NA) and the Leica DMI6000 B Inverted Robotic Microscope

Protection from the stratospheric ozone layer is essential to survival of plants, humans, animals, and other life forms of organisms on this planet. Depletion of stratospheric ozone, mainly due to man-made pollutants, such as chlorofluorocarbons and other halogenated ozone depleting substances, has resulted in the increased solar ultraviolet-B (UV-B, 280-315nm) radiation at high and mid-latitudes in both the Southern and Northern hemispheres [1, 2]. Trees growing under these conditions must have evolved strategies for coping with such detrimental stress in order to survive. The increased concentrations in leaf UV-B absorbing compounds, mainly flavonoids and related phenolics, may help protect and filter plants against the enhanced UV-B levels during the growing season. Research has shown that flavonoids and related phenolics play an important role in plant defense against UV-B radiation [3].

Leaf Anatomical Changes Induced by Paclobutrazol Tree Growth Regulator in Cherrybark Oak

Paclobutrazol (PBZ) is a commercial growth retardant developed for reducing tree growth along streets and under utility power lines. Our previous studies indicated PBZ treated cherrybark oak (Quercus falcata var. pagodafoila L.) exhibited smaller and thicker leaves, shorter leaf petioles, higher chlorophyll content, higher light absorbance, darker green foliage, and more compact crowns with improved gas exchange rates; and PBZ application significantly reduced the tree height and diameter growth in cherrybark oak [1, 2, 3, 4]. The improved physiological performance and reduced tree size can help enhance tree vigor and lower the pruning associated maintenance cost at the same time. Thus, applied properly, PBZ can be used as an effective tool in urban and community tree management. This paper took a closer look at the leaf anatomical changes induced by PBZ tree growth regulator in cherrybark oak, which is one of the major oak species and popular shade trees in the Southern USA.