XVI
ABSTRACT
STUDIES ON THE ANTI-INFLAMMATORY POTENTIAL OF COPAIBA OIL-RESIN FROM
COPAIFERA LANGSDORFFII
AND
ITS DITERPENE CONSTITUENT KAURENOIC ACID IN
EXPERIMENTAL MODELS OF INTESTINAL INFLAMMATION.
Laura Andréa Farias Paiva, thesis
submitted in partial fulfillment for the award of Degree in Doctor of Philosophy in Pharmacology, Post Graduate
Department of Physiology and Pharmacology, Faculty of Medicine, Federal University of Ceará, Fortaleza, CE,
Brazil. Advisor: Vietla Satyanarayana Rao.
Copaiba oil-resin from
Copaifera langsdorffii
(Leguminaceae) is a reputed traditional
remedy for the treatment of inflammatory conditions and to promote healing of ulcers and
wounds. Previous studies established its anti-inflammatory and gastroprotective properties
through animal experimentation. The present study extended these earlier studies to
analyse the intestinal anti-inflammatory potential of oil-resin
Copaifera langsdorffii
(ORCL)
and its diterpene constituent, kaurenoic acid (KA) in rat models of ulcerative colitis induced
by acetic acid (AA-UC), and trinitribenzene sulfonic acid (TNBS-UC), and in indomethacin -
and ischemia-reperfusion-induced intestinal inflammation (IND-II and I/R-II). Further, its
wound healing potential was evaluated in rats on open and incision wounds. Rats were
pretreated orally (15 hrs and 2 hrs before) or rectally 2 hrs before the induction of colitis
with ORCL (200 and 400 mg/kg), KA (50 and 100 mg/kg) or vehicle (1 ml, 2% Tween 80
or 1 ml, 2% DMSO). Colitis was induced by intracolonic instillation of a 2 ml of 4% (v/v)
acetic acid solution or TNBS (0.25 ml of 20 mg) and 24 hrs or 72 hrs latter, the colonic
mucosa was analysed for the severity of macroscopic colonic damage, the myeloperoxidase
and the malondialdehyde levels. In AA-UC model, a marked reduction in Gross damage
score and in wet weight/length ratio of colonic tissue were evident in animals pretreated
orally or rectally with test substances, as compared to vehicle alone-treated controls. This
effect was confirmed biochemically by a significant reduction in colonic myeloperoxidase
(MPO) activity, the marker of neutrophilic infiltration and by a marked decrease in
malondialdehyde (MDA) level, an indicator of lipoperoxidation. Besides, AA elevated
increase in the levels of nitrite and catalase activity in colon tissue was also significantly
decreased by ORCL treatment. Furthermore, microscopical examination revealed the
diminution of inflammatory cell infiltration, and the submucosal edema in colon segments
of rats pretreated with ORCL or KA. In a similar manner, in TNBS-UC, a marked reduction
in Gross damage score and in wet weight/length ratio of colonic tissue was evident by
ORCL pretreatment (400 mg/kg, p.o. or intra-rectal) at 2, 24 and 48 hrs after intracolonic
injection of TNBS. MPO activity but not the MDA and catalase levels were significantly
affected by ORCL treatment. Histological observations also indicated only a partial
protection by ORCL, suggesting that TNBS-UC being a chronic model, a more prolonged
therapy may be needed. In the model of I/R-II, five forty minute of ischemia followed by
one hour reperfusion of superior mesenteric artery caused significant elevations of MPO,
catalase, MDA and nitrite levels with a significant decrease in non-protein sulfhydryls (NP-
SH/ GSH) indicating an oxidative stress. These changes were significantly reversed by oral
pretreatment with ORCL (200 and 400 mg/kg), suggesting that ORCL obliterates oxidative
stress. Pretreatment of animals with ORCL (200 and 400 mg/kg, p.o.) or KA (100 mg/kg,
p.o.), 12 and 2 hrs before the administration of 20 mg/kg indomethacin mitigated the
intestinal toxicity as evidenced by decreases in tissue levels of MPO and nitrite. Unlike
indomethacin, ORCL but not KA at either dose failed to induce a significant increase in
intestinal permeability. This effect of ORCL simulated that of a selective COX-2 inhibitor,
rofecoxib. These observations suggest that ORCL is devoid of intestinal toxicity unlike the
classical non-selective COX inhibitors. Also, ORCL promoted wound healing in rats on
experimental open or incision wounds as evidenced by an early wound contraction and
increased wound tensile strength. The data indicate a significant anti-inflammatory
potential of copaiba oil-resin and its diterpenoid, kaurenoic acid possibly mediated through
an antioxidant/anti-lipoperoxidative mechanism(s).