Inhibitions of acute and chronic inflammations by Bixa orellana leaves extract

Bixa orellana or anatto is a fruiting shrub that belongs to Bixacea family. The leaves extracts have been shown to have anti-gonorrhoeal [1] and anti-microbial properties [2]. Recently, it was also proven to possess neuropharmacological, anticonvulsant, analgesic, antidiarrhoeal and antibacterial activities [3]. The objective of this study is to investigate the anti inflammatory activities of Bixa orellana leaves. Acute inflammation was induced in adult Sprague-Dawley rats using various inflammatory mediators. The paw edema model was employed for this study, whereby mediators such as carageenan, histamine, serotonin and bradykinin were injected into the rat hind paws to induce inflammation. 96 Sprague-Dawley rats were divided into 16 groups (4 groups per mediator) consisting of six rats per group respectively. Example of groupings is as follows: e.g. for carageenan, Group 1A (positive control group) was given 10mg/kg mefenamic acid orally, whereas group 1B was not treated but fed orally with distilled water as vehicle. The treated rats (group 1C & 1D) were treated respectively with 50 and 150mg/kg of aqueous extract of Bixa orellana (BOE) via oral administration. The treatments mentioned earlier were given once daily to all rats from every groups for 4 days. On the fourth day, the treatment was given orally 1 hour prior to injection of Carageenan (0.1ml of a 1% solution in 0.9% saline solution) into the plantar region of the right hind paw of each rat. For other mediators, specific antagonists were given to the positive control group, but the rest were treated similarly to the carageenan group. The paw volume was measured before the injection and each hour after for a period of 5 hours by means of volume displacement method by using plethysmometer. The average increase in paw volume of each group was calculated at every time point and compared statistically using one-way ANOVA. For carageenan, the paw volume of negative control rats had increased starting from 0hr and peaked at the second hour and then gradually declined during the 3rd to 5th hours. Significant inhibitions were seen in rats treated with Bixa orellana, group 1C &1D, at where the peak should be (p<0.05). Other mediators also induced paw swelling with various peaks. Histamine in group 2 caused maximum paw volume to be reached during the first hour and all treatments, histamine antagonist, Loratadine (group 2A), 50mg/kg BOE (2C) and 150mg/kg BOE (2D) significantly reduced their paw volumes at that hour (p<0.05). Serotonin also induced a peak at 1hour and the peak was abolished when treated with 5HT antagonist and BOE (group 3A, C & D) (p<0.05). Bradykinin similarly followed by inducing a peak at 30 mins and significant inhibitions were seen in groups treated with Ketoprofen and BOE (group 4A, C & D) (p<0.05). Another 4 groups of rats (n=6 per group) were used in the cotton-pellet granuloma test to induce chronic inflammation. Under light anaesthesia, a small cut was made onto the dorsal part on the right and left sides of each rats by using a sterile surgical blade. Upon incision, two sterile cotton pellet weighing±30mg were implanted inside the wound in the right and left sides of the dorsal part of each rat. The parted skin is further being sutured using a surgical thread and curved needle. The wound is left undressed for eight days to produce chronic inflammation and within that period of time each rats were treated similarly as the acute inflammation study. As sutures being removed on the eighth day, the degree of inflammation is measured by weighing the cotton wet weight and compared with the cotton dry weight. The cotton inside the wound may contain dead cells as well as transudates as the product of prolonged inflammation. The percentage of inhibition (anti-transudate and anti-proliferative) is highest in the rats treated with 150mg/kg of Bixa orellana extract and compared to non-treated rats. As a conclusion, this preliminary study has shown that Bixa orellana has proved to be an excellent anti-inflammatory agent not only in acute but chronic inflammation model as well.

References: [1] C Armando, M Herlinda, M Emilia and C Guillermo (1995) J Ethnopharmacol 48: 85–88. [2] TC Fleischer, EPK Ameade, MLK. Mensah and IK. Sawer (2003) Fitoterapia 74: 136–138. [3] JA Shilpia, M Taufiq-Ur-Rahmanb, SJ Uddinc, MS Alamc, SK Sadhud and V Seidela (2006) J Ethnopharmacol. 108 (2): 264–271.