Antiarthritic Activity Of Anthraquinones Found In Aloe Vera For Podiatric Medicine
By Robert H. Davis, Ph.D.; Patrick S. Agnew, B.S. & Eugene Shapiro, B.S.
Journal Of The American Podiatric Medical Assoc., Vol 76, Number 2, February 1986
Rheumatoid arthritis is a painful and crippling systemic disease for which there is no cure. The best experimental model for studying rheumatoid arthritis in humans is the adjuvant-induced arthritis in rats. One of the group of compounds found in Aloe is the anthraquinones. These substances have been recognized for their use in veterinary medicine against inflammation. The authors evaluate the anti-inflammatory and antiarthritic activity of anthraquinone, anthracene, cinnamic acid, and anthranilic acid found in the Aloe vera plant, and show what contribution each ingredient makes toward the total activity found in Aloe.
In previous studies, the authors have shown that Aloe gel extract has anti-inflammatory and antiarthritic activity.1 Combinations of Aloe with ascorbic acid, thymus extract, and RNA significantly improved the activity.2 The chemical makeup of Aloe holds a valuable key to antiarthritic activity that could be used by podiatrists to treat patients.3 Elements in Aloe gel include lignin, saponins, anthraquinones, inorganic ingredients / minerals, vitamins, enzymes, and amino acids. Anthraquinones such as anthracene have been recognized for their use in veterinary medicine against inflammation. They possess anti-inflammatory, analgesic, and tissue repair properties.
No doubt anthraquinones have a bearing on the healing and pain-killing effectiveness of the fresh leaf gel. Few people understand the meaning of the anthraquinone complex in Aloe. Many studies verify the successful treatment of burns, ulcers, and dermatitis, but no one knows why Aloe has these healing qualities.5 The authors propose to test the antiarthritic and anti-inflammatory activity of anthraquinone, anthracene, cinnamic acid, and anthranilic acid in an adjuvant arthritis model in order to determine if there are possible ingredients that can be used to treat rheumatoid arthritis. This approach will help us understand the antiarthritic activity of Aloe. The purpose of this study is to determine, in part, the active elements in Aloe so as to unlock the mystery of the gel. Many medicines in common use today, such as digitalis and quinidine, were derived in a similar way from barks and leaves.
Materials And Methods
Adult male Sprague-Dawley rats (175 to 200 gm, 12/group) were injected with heat-killed Mycobacterium butyricum. The bacteria were suspended in light mineral oil at 5 mg/ml. Under ether anesthesia, two groups of rats were injected in their right hind paw with 0.1 ml of oil. All the other groups were injected with the suspended bacteria. Six hours after the injections, the day 0 measurements were taken. Two experiments were conducted together. One study investigated the effect of anthraquinones on the prevention of adjuvant arthritis. The other study determined their effect on established adjuvant arthritis. Three control groups were used. The animals injected with oil alone were used to be sure that the oil, itself, did not cause swelling. One of the groups injected with adjuvant was also injected with distilled water at the same times and amounts as those groups being treated. This was done to determine whether the volume and frequency of injections affected the amount of swelling. A third group was injected with the adjuvant.
In the first experiment, prevention of adjuvant arthritis by anthraquinones was studied. The right hind paws of two control groups were injected with the adjuvant, and day 0 paw volume measurements were taken. One of the control groups was injected with 10 ml of water subcutaneously daily for 13 days beginning on day 0. Either anthraquinone, anthracene, cinnamic acid, or anthranilic acid was injected into rats in four other groups that had received M. butyricum. Each day the anthraquinones were injected subcutaneously at 150 mg/kg aqueous suspensions.
In the regression study, the rats were injected with M. butyricum suspension. The symptoms of adjuvant arthritis usually take from 14 to 21 days to develop. After 21 days, treatment was initiated with 150 mg/kg suspensions of anthraquinones subcutaneously daily from day 21 through day 33.
Adjuvant arthritis in rats manifests itself by swelling in all paws, especially the hind paws, gonads, and ears. A water plethysmograph was used to monitor the hind paw volume. The plethysmograph was at zero prior to each reading while maintaining constant sensitivity to obtain consistency. Edema in the injected (right) hind paw was considered to be inflammation caused by trauma. Prolonged inflammation in this paw was maintained by the slow release of the M. butyricum. Any edema in the left paw was considered to be an immunological phenomenon.6,7
The rats were anesthetized with ether on paw-measuring days. Their hind paw volumes were determined by dipping them into a fluid-filled cell up to the anatomical hair line. Day 0 measurements were taken 6 hours after the paws were injected with M. butyricum adjuvant or oil alone. This initial measurement was used as a reference from which units of edema were calculated in the prevention study. These units of edema were calculated by subtracting the day 0 volumes from those measured on days 7, 14, and 21. The base-line values for calculating units of edema in the regression study were measured on day 21. Day 21 values were viewed as 0 units of edema. The hind paws were measured on days 0, 21, 28, 35, and 38 for this study.
The animal’s body weight was measured on days 0 and 2l in both studies and day 38 in the regression study. The change in weight during the experiments was calculated by subtracting from day-38 weights in the regression experiment. The change in edema was divided by the change in weight to obtain a relative change in edema. This served to rule out any gain in paw volume caused by weight gain. A CU-5 Medical Land Camera was used to photograph representative rats on days 21 (prevention study) and 38 (regression study). This was done to demonstrate the difference in paw edema between the rats receiving anthraquinones and the control rats. Mean paw volumes and body weights were recorded for all animals. Standard errors were determined by using the formula SE = E d2/N(N - 1). The deviation of individual values from the mean is Ed2, and N - 1 represents the degrees of freedom.
Results And Discussion
Prevention of Arthritis. Aloe has antipyretic and anti-inflammatory activity that has been used to treat burns and skin conditions over the years. Splitting the leaves of Aloe and applying the gel directly to burns produces beneficial effects.8 The curative principle occurs within the pulp and rind of the leaf.9 The authors have administered fresh Aloe leaf extract to prevent or regress adjuvant arthritis. Aloe extract produced a 48% inhibition of inflammation and a 72% inhibition of the immune response (the arthritis) when 150 mg/kg of Aloe extract was administered
subcutaneously, daily, over 13 days as preventive measure.1
The anti-inflammatory and antiarthritic activity of the anthraquinones were tested to determine if they could prevent the formation of arthritis. An increase in volume of the right hind paw is an anti-inflammatory response to the presence of the adjuvant, whereas the swelling of the left hind paw is an autoimmune response, in part, against the animal’s own cartilage. Mycobacterium butyricum is similar to cartilage so that the immune response attacks both. Swelling occurs in both hind paws injected with adjuvant. This swelling continues to increase over the entire experimental period. Aqueous controls received equal amounts of water injections as those receiving injections of
anthraquinone. Since these animals swelled somewhat more than those receiving the adjuvant, the volume or the trauma of daily injections contributed to the disease process. In order to more accurately estimate the effect of the compounds under investigation, the response of anthraquinones was compared to the aqueous injected adjuvant controls.
| Figure 1 |
Prevention of adjuvant arthritis with anthraquinones. |
Forst and Davis10 have shown that anthranilic acid has antiarthritic activity. This compound is present in Aloe and was considered as an activity internal control so that the authors could be certain that the responses recorded in the study were real and not phantoms. Edema in the right hind paw (inflammation) was 40% less than the aqueous adjuvant control animals on day 21 (Table 1; Fig. 1). The left hind paw (immune) was 35.5% less than the controls. The percentage of inhibition by anthranilic acid corrected for body weight was 79.7% in the inflammatory paw and 42.4% in the immune paws. Tryptophane, an active anti-inflammatory compound, is produced from anthranilic acid. Previous work showed that tryptophane inhibited arthritis 75% in the immune paw.10 Anthranilic acid may work through tryptophane.
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