Chromones and anthrones from Aloe marlothii and Aloe rupestris

A phytochemical investigation of the leaf exudate of Aloe marlothii has resulted in the isolation of a new chromone (7-O-methylaloeresin A) and a new anthrone (5-hydroxyaloin A 6'-O-acetate). Furthermore 7-O-methylaloesin was isolated as a natural product for the first time from the leaf exudate of Aloe rupestris. The structure elucidation of these compounds was based on spectral data including 2D NMR. The chemotaxonomic value of 7-O-methylaloesin in Aloe series Asperifoliae and section Pachydendron is discussed.     

Three oxanthrones from Aloe littoralis

The leaf exudate of Aloe littoralis yielded, in addition to the known 10-hydroxyaloin B, two new C-glucoside oxanthrones namely 10-hydroxy-15-O-(2R,3S-nilyl)(6′-O-acetyl)aloin B (littoraloin) and 10-hydroxy-15-O-(2R,3S- nilyl)aloin B (deacetyllittoraloin). Their structures were determined by spectroscopic methods as well as by conversion to the known 10-hydroxyaloin B and nilic acid.     

Anthraquinone,anthrone and phenylpyrone components of Aloe nyeriensis var. kedongensis leaf exudate

The leaf exudate of Aloe nyeriensis var. kedongensis yielded six compounds which were identified on the basis of spectral data and inter-conversions as two groups of three allied compounds. These were (a) 4-methoxy-6(2′,4′-dihydroxy-6′- methylphenyl)-pyran-2-one, its 2′-O-β-D-glucopyranoside (aloenin) and the 2″-O-p-coumaroyl ester of aloenin, (b) the anthracene derivatives l,2,8-trihydroxy- 6-methylanthraquinone (nataloe-emodin), its 2-O-β-D-glucopyranosyl ester and the corresponding 10-C -β-D-glucopyranoside nataloin.     

Phytochemistry and antiglycation activity of Aloe sinkatana Reynolds

A new anthraquinone along with 10 known compounds were isolated from the leaves of Aloe sinkatana Reynolds (Aloaceae), and their structures were elucidated as the new compound 2,8-dihydroxy-6-(hydroxymethyl)-1-methoxyanthracene-9,10-dione (1) and the known compounds Aloe-emodin (2), feralolide (3), 1-hydroxy-5-methoxy-3-methyl-9,10 dihydroanthracene 9,10-dione (4), β-sitosterol (5), β-sitosterol with glycosidic bond (6), microdontin (7), homoaloins A (8) and B (9) and aloins A (10) and B (11). Characterization of compounds 1–9 was based on spectral analyses and comparison with reported data, particularly the new compound 1 was identified by 1D- and 2D NMR, mass spectroscopic and X-ray crystallography analyses. Antiglycation activity of the extracts and isolated compounds were carried out using the hemoglobin-δ-gluconolactone and glucose–bovine serum albumin assays. The results obtained showed that MeOH and EtOAc extracts as well as compound 1 showed an inhibitory effect on early stage protein glycation. Compound 1 also showed significant inhibitory effects against glucose-induced advanced glycation end-products.     

Chemical characterization of the immunomodulating polysaccharide of Aloe vera L

The polysaccharide isolated by alcohol precipitation of Aloe vera mucilaginous gel was found to have a Man:Glc:Gal:GalA:Fuc:Ara:Xyl ratio of 120:9:6:3:2:2:1 with traces of Rha and GlcA. Linkage analysis of the endo-(1-->4)-beta-d-mannanase-treated sample yielded Manp-(1--> (approximately 26%), 4-Manp (approximately 53%), 2,4-Manp (approximately 3%), 3,4-Manp (approximately 1%), 4,6-Manp (approximately 1%), 4-Glcp (approximately 5%), 4-Xylp (approximately 1%), Xylp-(1--> (approximately 2%), Galp-(1--> (approximately 5%), and traces of 4,6-Galp and 3,6-Galp. Hydrolysis with strong acids produced a mixture of short oligosaccharides and an acid-resistant fraction containing greater relative fractions of Manp-(1-->, Araf-(1-->, Xylp-(1-->, and 4-Xylp than the bulk polysaccharide. NMR analysis of oligosaccharides generated by endo-(1-->4)-beta-D-mannanase and acid hydrolysis showed the presence of di-, tri-, and tetrasaccharides of 4-beta-Manp, beta-Glcp-(1-->4)-Man, beta-Glcp-(1-->4)-beta-Manp-(1-->4)-Man, and beta-Manp-(1-->4)-[alpha-Galp-(1-->6)]-Man, consistent with a backbone containing alternating -->4)-beta-Manp-(1--> and -->4)-beta-Glcp-(1--> residues in a approximately 15:1 ratio. Analysis of the sample treated sequentially with endo-(1-->4)-beta-d-mannanase and alpha-D-galactosidase showed that the majority of alpha-Galp-(1--> residues were linked to O-2, O-3, or O-6 of -->4)-beta-Manp-(1--> residues, with approximately 16 -->4)-beta-Manp-(1--> residues between side chains. Our data provide direct evidence of a previously proposed glucomannan backbone, but draw into question previously proposed side-chain structures.     

Micropropagation of the endangered Aloe polyphylla

A rapid propagation protocol was establish for thehighly endangered Aloe polyphylla (Schönland ex Pillans). Seed was germinated in vitro on Murashige & Skoog 1962 medium [6] with or without sucrose. Plantlets were cultured onmedium containing benzyladenine only, or a combinationof BA and NAA. After initial problems with browning,the explants rapidly formed axillary and adventitiousbuds. Maximal shoot formation was obtained on MSmedium containing 1.0 mg l^–1 BA. Some shootsrooted spontaneously on MS medium, but the rootingpercentage was improved with a 0.5 mg l^–1 IBAsupplement. Rooted plantlets were acclimatized togreenhouse conditions. The success of this projectindicates that micropropagation can be a useful toolin the conservation of this endangered species of thegenus Aloe.     

The Relation Between Activity of Phosphoenolpyruvate Carboxykinase and Photosynthesis in Aloe vera Leaves

The chlorophyllous layer of leaf of a PEP-CK type CAM plant Aloe vera was stripped tiff from the colorIess water storage tissue and used to stuly the interrelation between the activity of decarboxylating enzyme phosphoenolpyruvate carboxykinase (PEPCK) and photosynthesis. Oxaloacetate, malate+ADP, and NaHCO3 were found to stimulate photosynthetic oxygen evolution. During the period from 6:00 to 18:00 of the day time, a diurnal fluctuation was observed in both PEPCK activity and the rate of oxygen evolution. The maximum of photosynthesis appeared at 10-12:00, but the maximum PEPCK activity appeared at 14:00. The PEPCK activity and photosynthetic rate in leaf discs increased with temperature from 10 to 35℃, then decreased at 45℃. Similar decline of both parameters was found in the leaf discs stressed by different concentration of PEG-6000 solution for 4.5 h. At light intensity of 900 mol m-2 s-1 and 25℃, the PEPCK activity and photosynthetic rate of leaf discs rised with the illumination time, then a slight inhibition followed at the time of 30 min (Pn) or 40 min (PEPCK). The strong response of PEPCK activity to high light intensity in leaf discs, and a progressive increase of PEPCK activity in direct illumination of crude enzyme extractm the range of 0-55 min, indicated that light s likely to be an activator for PEPCK. Leaf discs were infiltrated with 3-(3,4-dichlorophenyl)-l, 1-dimethylurea, DL-glyceraldehyde and 2,4-dimitrophenol resulted in the partial inhibition of light-ependent photosynthesis and decarboxylation of C4 acid. The activity of PEPCK was also stimulated by Mg2+ or Mg2++ATP infiltrated into the leaf discs in the dark. The evidence presented here suggested that PEPCK activity of CAM plants showed a close interrelation with photosynthesis. Both of them were regulated by the environmental changes. The activity of PEPCK might be coupled to electron trsnsport and photophosphorylatiou.     

A chemotaxonomic and morphological appraisal of Aloe series Purpurascentes, Aloe section Anguialoe and their hybrid, Aloe broomii

Evidence is presented to suggest the hybrid origin of Aloe broomii, with the one putative parent belonging to Aloe series Purpurascentes and the other a member of Aloe series Anguialoe. A chemotaxonomic and morphological assessment is presented for both infrageneric groups and their hypothesised hybrid. Four of the species belonging to the series Purpurascentes display a characteristic leaf exudate profile containing the chemotaxonomic marker microstigmin. Aloe gariepensis and A. succotrina lack the diagnostic leaf exudate compounds. The distinct morphological apomorphies for Aloe section Anguialoe are supported on the chemical level reinforcing the monophyly of this group.     

Effect of Aloe vera gel extract on antioxidant enzymes and azoxymethane-induced oxidative stress in rats

The present work was undertaken with a view to study the effect of oral feeding of 2% Aloe vera gel extract (AGE) for 30 days on azoxymethane (AOM)-induced oxidative stress in rats. It was observed that AOM administration resulted in a significant increase in malondialdehyde and conjugated dienes, with reduction in hepatic glutathione (GSH), vitamin A and uric acid contents. AOM-induced reduction in hepatic GSH and uric acid was brought back to normal by AGE. There was a significant raise in hepatic catalase, superoxide dismutase and glucose-6-phosphate dehydrogenase (G-6-PD) activities as a result of feeding of the extract. Ingestion of the extract effected reduction in AOM-induced colonic GSH-peroxidase, G-6-PD and glutathione S-transferase and femur bone marrow micronuclei formation. Hence, it is suggested that Aloe vera gel extract possess the ability to reduce AOM- induced oxidative stress and toxicity in liver.     

Biochemical studies of Aloe vera (Aloe barbadensis Miller) gel of the field grown and micropropagated plants at different developmental stages

The biochemical composition of leaf gel isolated from vegetative and micropropagated Aloe vera plants at different stages of development had been compared. The total sugars, fructose, sucrose and starch were higher in micropropagated leaf gel at all developmental stages. The micropropagated plants have higher α-amylase activity at all stages with maximum at 6 month old. Catalase and peroxidase activities were higher in younger leaves (up to 4 month old) in both types of plants. The calcium and magnesium level increases up to maturity and ranges from 0.19 to 1.12% and 0.02 to 0.10% respectively, in conventionally grown plants whereas it was a little higher in micropropagated plants. Micropropagated plants had 12.5% higher phosphorus levels. The micropropagated plants (1 month old) have 60% higher phenol content as compared to conventional plants. The micropropagated mature plants have 55 and 18.6% higher saponin and sterol contents as compared to conventional plants. The composition of aloe vera gel depends upon the growth stages and method of propagation.     

A Comparison of Anther Tissue Development in Male Sterile Aloe vera and Male Fertile Aloe ciliaris

Cytological differences between the anther development of amale sterile and a male fertile Aloe species are used to explaininteractions between anther tissues. Some deviations in thelayers of the locule wall and the microspores of the male sterileanther are related to each other and their biological functionsare discussed. The cytological development of the male sterility,which can be observed shortly after meiosis, seems to be restrictedto the locular cavity. The tapetal development and breakdownare normal, apart from the size of some orbicules. However,the pollenkitt is not transported to the pollengrains, whichstrongly supports our theory that this process is mechanicallypollen-controlled. The development of the epidermal and endothecialcells is normal, except in a part of the anthers where thesecells do not expand, after which dehiscence is incomplete. Thelatter process is discussed in relation to the deviations insidethe locular cavity. Aloe vera (L.) Burm. fil., Aloe ciliaris Haw., Liliaceae, male sterility, tapetum, pollenkitt, endothecium, anther dehiscence     

Isolation and identification of a phenolic antioxidant from Aloe barbadensis

A potent antioxidative compound has been isolated from a methanolic extract of Aloe barbadensis Miller using a combination of column and thin-layer chromatography. The antioxidant activity of this substance was similar to that of alpha-tocopherol as assessed in vitro using rat brain homogenates. On the basis of electrospray ionization and electron-impact ionization mass spectra in combination with reversed-phase, high-performance liquid chromatographic behavior, this compound has been identified as 8-C-beta-D-[2-O-(E)-coumaroyl]glucopyranosyl-2-[2-hydroxy]-propyl-7-methoxy-5-methylchromone.     

Graphene oxide exhibited positive effects on the growth of Aloe vera L

There is increasing evidence for graphene associated plant growth promotion, however, the chronic effects of soil-applied graphene remain largely unexplored. The present study investigated the morphological, physiological and biochemical responses of graphene oxide (GO) on Aloe vera L. over the concentration range of 0–100 mg/L for four months. Our results demonstrated that GO, with the best efficiency at 50 mg/L, could enhance the photosynthetic capacity of leaves, increase the yield and morphological characters of root and leaf, improve the nutrient (protein and amino acid) contents of leaf, without reducing the content of the main bioactive compound aloin. Compared with leaves, the effect of GO on root growth was more obvious. Although the electrolyte leakage and MDA content were raised at high concentrations, GO treatment did not increase the root antioxidant enzymes activity or decrease the root vigor, which excluding typical stress response. Furthermore, injection experiments showed that the GO in vivo did not change the plant growth state obviously. Taken together, our study revealed the role of GO in promoting Aloe vera growth by stimulating root growth and photosynthesis, which would provide theory basis for GO application in agriculture and forestry.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-021-00979-3.     

Expression of biologically active human interferon alpha 2 in Aloe vera

Methods necessary for the successful transformation and regeneration of Aloe vera were developed and used to express the human protein, interferon alpha 2 (IFN??2). IFN??2 is a secreted cytokine that plays a vital role in regulating the cellular response to viral infection. Transgenic plants were regenerated from callus cultures initiated from zygotic embryos. Expression of the IFNA2 transgene in transformed plants was confirmed by RT-PCR and IFN??2 protein was detected by immunoblot analysis. Human A549 cells treated with transgenic aloe extracts for 6?h induced expression of the interferon stimulated gene 54, indicating activation of the IFN signaling pathway. The biological activity of the aloe produced IFN??2 was assessed using an antiviral assay with A549 cells treated with extracts from both the rind and pulp fractions of the shoot and subsequently infected with the lytic encephalomyocarditis virus. The highest level of activity attributable to recombinant IFN??2 was determined to be 625?IU/mg of total soluble protein (TSP) in the rind and 2,108?IU/mg TSP in the pulp. Two daughter plants that vegetatively budded during the course of this study were also confirmed to express IFN??2. These results confirm that Aloe vera is capable of expressing a human protein with biological activity, and that a secreted protein targeting the apoplast can be detected in the pulp fraction of the plant.     

芦荟属14种2变种植物的核型分析

报道了芦荟属14种2变种植物的核型,实验结果表明所研究种类的体细胞染色体基数均为X=7,二倍体,由4对长染色体和3对短染色体组成。根据Stebbins（1971）的核型分类标准,Aloeaffinis Berger等3种芦荟的核型为“3B”型,Aloe graciliflora Groenewald等3种芦荟的核型为“4B”型,A．mitriformis Mill等3种2变种芦荟的核型为“3C”型,A．saponaria（Air．）Haw等5种芦荟的核型为“4c”型。其中有6种1变种芦荟的核型为首次报道。另外,还对芦荟的系统分类进行了讨论。     

Tissue Culture Propagation of Elite Plant of Aloe vera Linn

Micropropagation protocol for an elite selection of Aloe vera syn A. barbadensis through enhanced axillary branching was standardized. Murashige and Skoog medium containing 1 mg l^?1 BA and 0.2 mg l^-1 IBA gave highest multiplication. Citric acid at 10mg l^-1 and liquid medium improved the shoot multiplication. Hundred per cent microshoots produced rooted plantlets within 15 days of culture on hormone-free agar medium. Liquid medium during rooting stage decreased the number of shoots showing rooting response. The plants were successfully transferred in the soil and were morphologically similar to mother plants.     

Promotion proliferation effect of a polysaccharide from Aloe barbadensis Miller on human fibroblasts in vitro

A polysaccharide fraction was isolated from fresh Aloe barbadensis Miller leaves, which can promote the wound healing of the superficial II scald model mice. The monosaccharide composition and linkage determination were investigated by methylation and GC–MS, acetylation and GC, ¹³C NMR and DEPT. The results show that its glycosyl components contain d-glucose, d-galactose, d-xylose in a molar ratio of 5:5:1, and the API consists of a backbone of →2)-α-d-Galp-(1 → 2)-α-d-Glcp-(1→, having a branch of α-d-xylofuranosyl residue that is (1 → 3) linkage at O-3 of α-d-galactopyranosyl residue. It was found that the API could enhance proliferation of the human fibroblasts in vitro. The mechanisms of promotion proliferation were studied preliminarily.     

芦荟多糖含量测定及芦荟膏体外透皮吸收的实验研究

目的:研究芦荟膏中各功能成分体外透皮吸收的能力。方法:以Wistar大鼠的背部皮肤为透皮实验原料,每隔一定时间通过分光光度法和高效液相色谱法测定透皮后接收池内芦荟多糖及蒽醌类含量。结果:随着芦荟膏剂量的增加,渗透量逐渐增加,芦荟膏中芦荟多糖、芦荟大黄素、芦荟苷的渗透量随时间延长逐渐增加,但是渗透速率逐渐降低。结论:芦荟膏有较强的体外透皮吸收能力,芦荟膏经皮给药能充分发挥其作用。     

505. Aloe Parvula

Summary.  Aloe parvula A. Berger, a miniature aloe endemic to Madagascar, is described and illustrated. Its ecology and conservation status are discussed. A typical habitat in the Itremo Massif is shown.