Rheological, functional and morphological characterization of reconstituted Aloe vera gels at different levels of pH and concentration: Novel concepts of reconstituted Aloe vera gels formation.

In this study, firstly, gelation process and its optimization at different pH (3-7) and concentration (0.2-1.6%, w/v) on the viscoelastic behavior of reconstituted Aloe vera (A. vera) samples were studied using response surface methodology (RSM). The optimum condition obtained by numerical optimization for the formulation of reconstituted samples was 1.6%, w/v at pH 7 with desirability of 0.84. Secondly, structural alteration of the reconstituted A. vera gels were evaluated using FTIR, SEM, and TEM at particular pH (3-7) and concentration (0.2-1.6%, w/v). The FTIR spectrum of reconstituted hydrogels showed formation of new hydrogen bond at 3600-3000 cm-1 and deacetylation of acemannan at 1740 cm-1 with increase in A. vera concentration. Moreover, SEM and TEM micrograph images of A. vera xerogel at lower concentrations (0.2-0.4%, w/v) evidenced the intact surface morphology and formation of clumps and at higher concentration (0.8-1.6%, w/v), exhibited rope-like network patterns and composed of spherical aggregates.

The foliar anatomy and micromorphology of Aloe ferox Mill. (Asphodelaceae).

BACKGROUND: The genus Aloe has been the subject of several chemotaxonomic and phytochemical investigations. Aloe ferox is an important source of biologically active compounds like anthrones, chromones, pyrones, and flavonoids. It is a plant used extensively in traditional medicine. Despite the myriad of studies on the pharmacological profile of the plant, there still exists a dearth of scientific literature on the anatomical and morphological attributes of this important medicinal plant. MATERIALS AND METHODS: Hence, the objective of this study was to examine the foliar anatomy and micromorphological characteristics of A. ferox using light microscope and scanning electron microscope and to determine the elemental composition of the leaf sections by energy dispersive x-ray spectroscopy. RESULTS: Epidermal cells varied from round, square to hexagonal, with distinctive anticlinal walls and sunken stomata, equally distributed on both the adaxial and abaxial surfaces were observed. There were vertically elongated palisade cells with numerous chloroplasts in the palisade mesophyll layer. The EDXS analysis revealed Ca, K, S, Al, Mg, and Si as the major constituents of crystals present in the mesophyll. CONCLUSION: Information on the foliar anatomy and micromorphology can further enlightened our perceptions on the inherent interrelationships between structure and function as regards the synthesis and secretion of bioactive secondary metabolites by plants.

Determinación de macro elementos en exudado de hojas de zábila (Aloe vera (L.) Burm. f.) / Macroelements determination in zabila leaves exudate (Aloe vera (L.) Burm. f.)

El Aloe vera (L.) Burm. f. (zábila) es una planta utilizada por sus propiedades medicinales, la parte utilizada de esta planta es su hoja, de ésta se extraen dos componentes: los cristales y el exudado. En esta investigación se estudió la concentración de macro elementos presentes en el exuda-do de hojas de zábila, a saber: sodio (Na), calcio (Ca), magnesio (Mg) y potasio (k) por espectrometría de absorción atómica en llama (FAAS). Las plantas estudiadas fueron cultivadas en la ciudad de Coro, estado Falcón. Las muestras compuestas de exudado se recolectaron en hojas ubi-cadas en las posiciones bajas, medias y superiores de las plantas. Luego se secaron por liofilización, y se mineralizaron: 0.25 g de muestra de exudado se sometieron a digestión ácida, con 1:2 HNO3 concentrado y H2O2 en plancha de calentamiento. Se utilizó material certificado NIST 1572, USA: Hojas de plantas cítricas, para evaluar la exactitud del método, no encontrándose diferencias estadísticamente significativas (p <0.05) entre los valores del material de referencia con los valores obtenidos con el método aplicado en esta investigación. El promedio de la desviación estándar relativa (RSD) fue de 1.41%, lo que certifica la precisión del método empleado. Las concentraciones de los macro elementos encontradas fueron: Na: 0.24 ± 0,03% p/p, k: 0.69 ± 0,13% p/p, Ca: 0.07 ± 0,01% p/p y Mg: 0.01 ± 0,00% p/p. El método empleado para determinar la concentración de Na, Ca, Mg y k en muestras de exudado de zábila por FAAS fue exacto, preciso y libre de interferencias.

The objective of this work was to determine the metals in Aloe vera (L.) Burm. f. (zabila). Theses metals are necessary in the human organism; namely: Na, k, Ca y Mg. It was digested for 1 hour in a hot plate at 70 ºC 0.25 g of lyo-philized exudate with 1:2 nitric acidic and hydrogen peroxi-de. It was no found significatives statistics differences at 95% of confidence between the standard calibration curve and the aqueous calibration curve, so no matrix effect was observed. The recovery studies was satisfactory, the mean value was 99.77 ± 2%. It was no found significatives statistics differences at 95% of confidence between the certificated values (NBS: Citrics leaves 1572) of studied metals and the values found with the applied methodology. The concentrations of these elements in the real composed samples were: Na: 0.24 ± 0,03% w/w; k: 0.69 ± 0,13% w/w; Ca: 0.07 ± 0,01% w/w; Mg: 0.01 ± 0,00% w/w. The method used to determine the determined elements was exact, pre-cise and free from interferences.

[Effects of enhanced UV-B radiation on leaf anthraquinones content and cell ultrastructure of Aloe vera L].

By using transmission electron microscopy and high performance liquid chromatography, this paper studied the effects of enhanced UV-B radiation on the leaf anthraquinones content and cell ultrastructure of Aloe vera L. After treated with enhanced UV-B radiation 6 hours per day for 20 days, the total anthraquinone content, barbaloin content, and aloe-emondin content in A. vera leaves increased by 31.8%, 11.3%, and 22.0%, respectively, chloroplast envelope membrane was slightly damaged, but the structure of other organelles had no significant change. It was suggested that UV-B radiation could promote the accumulation of anthraquinone in A. vera leaves, but had less effects on the leaf cell ultrastructure.

A novel method for air drying aloe leaf slices by covering with filter papers as a shrink-proof layer.

To prevent the shrinkage of aloe vera slices during air drying, a method utilizing a shrink-proof layer was developed. The sample was configured of whole leaf aloe slices, where 1 side or both sides were covered with filter papers as shrink-proof layers. After air drying by varying the air temperature and the slice thickness, the drying characteristics, as well as several quality factors of the dried aloe vera leaf slices, were analyzed. In the simulation of the drying curves, the modified Page model showed the best fitness, representing a diffusion-controlled drying mechanism. Nonetheless, there was a trace of a constant-rate drying period in the samples dried by the method. Shrinkage was greatly reduced, and the rehydration ratios increased by approximately 50%. Scanning electron microscopic analysis revealed that the surface structure of original fibrous form was well sustained. FT-IR characteristics showed that the dried samples could sustain aloe polysaccharide acetylation. Furthermore, the functional properties of the dried slices including water holding capacity, swelling, and fat absorption capability were improved, and polysaccharide retention levels increased by 20% to 30%. Therefore, we concluded that application of shrink-proof layers on aloe slices provides a novel way to overcome the shrinkage problems commonly found in air drying, thereby improving their functional properties with less cost. Practical Application: This research article demonstrates a novel air drying method using shrink-proof layers to prevent the shrinkage of aloe slices. We analyzed extensively the characteristics of shrinkage mechanism and physical properties of aloe flesh gels in this drying system. We concluded that this method can be a beneficial means to retain the functional properties of dried aloe, and a potential alternative to freeze drying, which is still costly.

[Ultracytochemical studies of aloin in Aloe arborescens leaves].

Lead acetate precipitation method was used for ultracytochemical localization of aloin. The processes of aloin production, transport and storage were studied by transmission electron microscope. Results showed that aloin was produced in the plastids of the assimilating tissue. The aloin was transported through the plastid membrane to the surrounding endoplasmic reticulum and enveloped in the vesicles by the endoplasmic reticulum elements, the vesicles approached and later fused with the plasmalemma. Some vesicles of the plastid membrane directly fused with the plasmalemma. The vesicles released their contents into the apoplast through exocytosis, and finally reached the vascular bundle sheath by apoplastic translocation. Aloin was transported to the internal tangential wall of vascular bundle sheath cell through endoplasmic reticulum vesicles, and reached the cytoplasm of aloin cell by means of plasmodesmata. Finally, aloin was stored in the vacuoles of aloin cell.

Nutritional content of fresh, bee-collected and stored pollen of Aloe greatheadii var. davyana (Asphodelaceae).

Aloe greatheadii var. davyana is the most important indigenous South African bee plant. Fresh, bee-collected and stored pollen of this aloe was collected and analysed for its nutritional content, including amino acid and fatty acid composition. Highly significant differences were found between the three types of pollen. Collection and storage by the bees resulted in increased water (13-21% wet weight) and carbohydrate content (35-61% dry weight), with a resultant decrease in crude protein (51-28% dry weight) and lipid content (10-8% dry weight). Essential amino acids were present in equal or higher amounts than the required minimum levels for honeybee development, with the exception of tryptophan. Fatty acids comprised a higher proportion of total lipid in fresh pollen than in bee-collected and stored pollen. This study is the first to compare the changes that occur in pollen of a single species after collection by honeybees.

Synthesis of gold nanotriangles and silver nanoparticles using Aloe vera plant extract.

Biogenic gold nanotriangles and spherical silver nanoparticles were synthesized by a simple procedure using Aloe vera leaf extract as the reducing agent. This procedure offers control over the size of the gold nanotriangle and thereby a handle to tune their optical properties, particularly the position of the longitudinal surface plasmon resonance. The kinetics of gold nanotriangle formation was followed by UV-vis-NIR absorption spectroscopy and transmission electron microscopy (TEM). The effect of reducing agent concentration in the reaction mixture on the yield and size of the gold nanotriangles was studied using transmission electron microscopy. Monitoring the formation of gold nanotriangles as a function of time using TEM reveals that multiply twinned particles (MTPs) play an important role in the formation of gold nanotriangles. It is observed that the slow rate of the reaction along with the shape directing effect of the constituents of the extract are responsible for the formation of single crystalline gold nanotriangles. Reduction of silver ions by Aloe vera extract however, led to the formation of spherical silver nanoparticles of 15.2 nm +/- 4.2 nm size.

Optical properties of rhodoxanthin accumulated in Aloe arborescens Mill. leaves under high-light stress with special reference to its photoprotective function.

In Aloe arborescens Mill. leaves, strong sunlight or its combination with drought induces the accumulation of the red keto-carotenoid, rhodoxanthin. Simultaneously, the transformation of chloroplasts into chromoplasts accompanied by degradation of thylakoid membranes and formation of plastoglobuli, large in size and number, takes place. Depending on stress conditions the build up of rhodoxantin occurred along with the loss of chlorophyll or on the background of relatively high content of the pigment in the leaves. Microspectrophotometrical measurements showed the presence of chlorophyll-free plastids and retention of carotenoids during leaf adaptation to strong sunlight. The plastid spectra contained absorption bands of common for higher plants carotenoids together with those of rhodoxantin, with absorption maxima situated in the blue (440-480 nm) and the green ranges of the spectrum, respectively. The studies of whole-leaf optical properties revealed a broad band of rhodoxanthin absorption in the blue-green range peaking near 540-550 nm. Within this spectral band the accumulation of rhodoxanthin occurring, probably, in plastoglobuli considerably increased light absorption by stressed Aloe leaves. A possible photoprotective function of rhodoxanthin and other carotenoids as an internal light trap analogous to that accomplished by anthocyanins in other plant species is discussed.

Isolation and characterization of structural components of Aloe vera L. leaf pulp.

The clear pulp, also known as inner gel, of Aloe vera L. leaf is widely used in various medical, cosmetic and nutraceutical applications. Many beneficial effects of this plant have been attributed to the polysaccharides present in the pulp. However, discrepancies exist regarding the composition of pulp polysaccharide species and an understanding of pulp structure in relation to its chemical composition has been lacking. Thus, we examined pulp structure, isolated structural components and determined their carbohydrate compositions along with analyzing a partially purified pulp-based product (Acemannan hydrogel) used to make Carrisyn hydrogel wound dressing. Light and electron microscopy showed that the pulp consisted of large clear mesophyll cells with a diameter as large as 1000 microm. These cells were composed of cell walls and cell membranes along with a very limited number of degenerated cellular organelles. No intact cellular organelles were found in mesophyll cells. Following disruption of pulp by homogenization, three components were isolated by sequential centrifugation. They were thin clear sheets, microparticles and a viscous liquid gel, which corresponded to cell wall, degenerated cellular organelles and liquid content of mesophyll cells based on morphological and chemical analysis. These three components accounted for 16.2% (+/-3.8), 0.70% (+/-0) and 83.1% of the pulp on a dry weight basis. The carbohydrate composition of each component was distinct; liquid gel contained mannan, microparticles contained galactose-rich polysaccharide(s) and cell walls contained an unusually high level of galacturonic acid (34%, w/w; Gal A). The same three components were also found in Acemannan Hydrogel with mannan as the predominant component. Thus, different pulp structural components are associated with different polysaccharides and thus may potentially be different functionally. These findings may help lay a basis for further studies and development of better controlled processing methods and applications for this well-accepted medicinal plant.