Lectin-like substances of fresh leaves of Aloe barbadensis Miller (=A. vera Burm.f.) and Aloe saponaria (Ait.) Haw. and the commercially 'stabilized' A. vera gel were investigated (Winters etal, 1981; Winters, 1993). Leaf extract fractions (Low speed supernatant; SI, High speed supernatant; SII and Highspeed pellet; HP), were prepared by differential centrifugation and examined by immunodiffusion-like precipitation and hemagglutin-ation assay. Fractions of fresh leaf extracts and the commercially 'stabilized' A. vera gel had high levels of lectin-like substances and substances in fluid fractions from both fresh leaf sources were found to markedly promote attachment and growth of human normal, but not tumor, cells and to enhance healing of wounded cell monolayers.
Fresh leaf homogenate, a mixture of juice and particles approximately 2 mm in size, was centrifuged at 4 °C and the greenish colored particle-free liquid supernatant was collected (SI fraction). Pelleted materials were recentrifuged at high speed at 10 °C. The high speed supernatant (SII fraction) and pellet (HP fraction) were individually collected. SI and SII fractions were dialysed and then concentrated at 4 °C. A commercially 'stabilized' A. vera gel was homogenized and separated into fractions as described for the fresh aloe leaf specimens. SI and SII fractions from this aloe source were then concentrated and refrigerated at 4 °C together with all other aloe fractions.
Biological and pharmacological activity. i Hemagglutinating and precipitating activities
Hemagglutination assays were carried out toward human and canine erythrocytes and concentrated SI and SII fractions were found to have the hemagglutinating activity.
Concentrated SI fraction of A. barbadensis contained markedly higher amounts of hemagglutination reactive substances than comparable fractions from A. saponaria or A. vera gel. Human erythrocytes were more sensitive indicators of hemagglutination than canine erythrocytes for tests of aloe fractions.
Precipitation tests were carried out toward human, canine and baboon sera and concentrated SI fractions from all three aloe sources reacted with human and baboon sera. In contrast, none of the aloe fractions reacted in the precipitation tests with canine sera from normal and tumor-bearing adult dogs (Winters, 1981). Concentrated SII from the three aloe specimens did not show immunoprecipitation reactions with any sera.
Biological and pharmacological activity. ii Effects of the aloe extracts on cell attachment, growth and wound healing
Human normal fetal lung and human cervical carcinoma cells in single-cell suspensions were aggregated by fractions of A. barbadensis having their high lectin-like activities. A dilution (1:10) of concentrated SI fraction caused a marked enhancement of attachment of human normal fetal lung cells but not human cervical carcinoma cells. There were no differences in cell attachment with the other A. barbadensis fractions compared with that of untreated control cells.
Biological and pharmacological activity. iii Enhancement of growth
Fractions SI and HP of A. barbadensis markedly enhanced the growth of human normal fetal lung cells treated in suspension and in monolayer cultures. Human cervical carcinoma cells treated in suspension cultures with the two fractions did not grow as well as untreated control cells, while the growth of the cells treated in monolayer cultures did not different from that of untreated control cells.
Biological and pharmacological activity. iv Wound healing model in monolayer culture
The number of cells at the edges of wounds in monolayer human normal fetal lung and human cervical carcinoma cells cultures treated with fraction SI of A. barbadensis were observed to be higher than cell densities at the wound edges in other cultures treated with SII and HP fractions and in untreated control cultures. In vitro wounded cell monolayer assays were performed as follows. Parallel lanes were scraped on confluent plate cultures while viewed through a dissecting microscope and the border between the monolayer and scraped area was considered wounded. Cell densities at the edges of the wounds, which reflected the rate of cell movement into the wound area, were counted.
Fractions of 'stabilized' A. vera gel inhibited attachment of cells treated in suspension and cell detachment in monolayer cultures of human normal fetal lung and human cervical carcinoma cells. Accordingly, these cytotoxic responses prevented the completion of cell attachment and growth experiments with fractions of 'stabilized' A. vera gel.
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