In this study

In this study, the potential anti-nociceptive and anti-inflammatory effects of crude methanolic extract and solvent fractions of Cucumis ficifolius was investigated using different animal models. In the acetic acid, hot plate and formalin nociception models the test substance significantly provided pain protection. In addition, the anti-inflammatory activity was investigated using carrageenan induced paw edema model.
The 80 % methanolic extract exhibited greater analgesic and anti-inflammatory activities than aqueous and butanol fractions; active principle(s) responsible for the anti-inflammatory activity might be available in this extract. In addition, higher reduction of paw edema and pain protection was observed in butanol than aqueous fraction. The superior efficacy of crude extract and butanol fraction suggests there is possibly a higher presence of phyotoconstituents with anti-inflammatory and analgesic activity in medium polar (butanol) and high polar (80 % methanol) solvents.
The abdominal constrictions response induced by acetic acid is a sensitive procedure to evaluate peripherally acting analgesics and primary tool for screening analgesic potential of test compounds (Mallam et al., 2016). Intraperitoneal injection of acetic acid causes irritation in the peritoneal cavity where various endogenous inflammatory mediators such as histamine, serotonin, bradykinin substance P, and prostaglandins are released. These inflammatory mediatory sensitize C fibers in acetic acid induced visceral pain (Connor et al., 2000; Afify et al., 2017). The Stimulation of the nerve endings of the primary afferent nerves produces pain characterized by constriction of abdominal muscle with extension of the fore limbs and elongation of the body (Connor et al., 2000; Mallam et al., 2016). Analgesic effect of the crude extract and solvent fractions in this study may be linked to C fibers mediated via inhibition of prostaglandins histamine, serotonin bradykinin and substance P.
The second pain model used was the hot plate test which is thermic stimuli involving stimulation of A? fibers. In this test two behavioral responses namely, paw licking and jumping are produced. The two response are supraspinally integrated and sensitive to opioid analgesics (Connor et al., 2000; Adebayo et al., 2014; Mallam et al., 2016; Afify et al., 2017). The plate was maintained at 55 OC, and at this temperature only opioid like agents are active (Debebe et al., 2007). In agreement with this, morphine produced a significant analgesia at all times of observation. It was selected as a reference drug by considering its advantages like provision of longer analgesia and lesser variability of response among animals (Dubuison and Dennis, 2006)
The maximum dose (800mg/kg) of methanol extract achieved maximum prolongation of reaction time at the point of time like morphine. However, the lowest and middle doses (200mg/kg and 400 mg/kg) produced maximum protection later on the course of observation (120 min) (Table 4). The 200 mg/kg butanol fraction exhibited more protection at 60 min. Variation in effect may be attributed to the plasma concentration of the test substances (Lighthall et al., 1999). Over all, methanol extract and solvent fractions elicited a considerable nociception latency comparing to the reaction time values to thermal stimulus in the negative control group. Presumably, the effectiveness of the methanolic extract and solvent fractions of the root of C. ficifolius observed in the present study could be due to an opioid action via A? fibers.
The third model used to measure analgesic activity of the experimental plant was formalin test. The formalin test in mice is a valid and reliable model of nociception and is sensitive for various classes of analgesic drugs. Injection of diluted formalin with the sub-plantar rout in to the dorsal surface of the hind paw produces unambiguous nociception reaction: paw licking (Hunskaar and Hole, 1987). Unlike other pain models, formalin test provides a number of advantages such as, little or no restraint, unhindered observation of the complete range of behavioral responses, and greater resemblance to clinical pain (Dubuisson, 1977; Hunskaar et al., 1986; Hasanein et al., 2007).
Following injection of formalin two phases of behavioral responses were observed. This is an indication that the nociception response has biphasic nature with different pain pathways. The early phase (neurogenic that involves stimulation of nociceptors directly by a chemical and detected by central nociceptive afferent terminals stimulating the A? fibers. The second phase is an inflammatory response due to direct stimulation of chemical nociceptors resulting in an increased input from C fibers (Hunskaar et al., 1985; Kamei, 1997; Meunier et al., 1998; Hasanein et al., 2007; Afify et al., 2017). The nociception response in the initial phase was recorded from 0-5 minutes while the late phase was recorded from 15-30 minutes (Kamei, 1997; Santos et al., 1998; Adedapo et al., 2014)
The late phase of formalin induced licking behavior is partly mediated by prostaglandins and can be inhibited by NSAIDs and steroids, as well as the centrally acting drugs (Hunskaar and Hole, 1987). Substance P and bradykinin participate in the manifestation of the first phase response, whereas histamine, serotonin, prostaglandin and bradykinin are involved in the second phase (Chung et al., 2000).
The presence of edema is one of the prime signs of inflammation. Carrageenan-induced paw edema is a well-defined model of acute inflammation that a variety of inflammatory mediators participates in its development (Sadeghi et al., 2011). The evolution of carrageenan induced acute inflammation is characterized by two phases, namely initial and late phases (Sangeetha, 2015).
Following injection of carrageenan, inflammatory mediators such as bradykinin, serotonin and histamine are released and contribute the initial phase that occurs between 0 and 2.5 h (Samad, 2001; Masresha et al., 2012; Rauf et al., 2014; Sangeetha, 2015). As indicated in Table 7 maximum peak of edema was observed at (180 min) which is thought to be due to the release of kinin-like substances, especially of bradykinin (Sangeetha, 2015). The second phase of edema is a result of overproduction of prostaglandins in tissues and may occur from 2.5 to 6 h post-carrageenan injection (Masresha et al., 2012).
The treatments achieved maximum anti-inflammatory activity at the four hour. This is supported by reports that the second phase is known to be sensitive to most clinically effective anti-inflammatory drugs (Sangeetha, 2015). Production of arachidonic metabolites via the COX-2 enzyme is the main factor responsible for the late phase of carrageenan induced inflammation (Yonathan et al., 2006), but not to lipoxygenase inhibitors (Masresha et al., 2012).
Based on the result of the present study, methanolic crude extract, aqueous and butanol fractions of C. ficifolius significantly decreased paw edema in both phases of carrageenan induced acute inflammation. This suggests bioactive constituents in the crude extract and solvent fractions may suppress both phases of acute inflammation by inhibiting the release and/or activity of the inflammatory mediators such as, bradykinin, histamine, and serotonin in the initial phase. In the late phase, a reduction in edema may be attributed to COX inhibitory action of 80% methanol extract and solvent fractions.
Preliminary phytochemical screening demonstrated the presence of phenols, flavonoids, terpinoids, steroids and saponins (Efrem et al., 2017) in hydro-alcoholic extract of C. ficifolius. The anti-nociceptive and anti-inflammatory effect of many plants has been attributed to their flavonoid, terpenoid, tannin, phenol, steroid, alkaloid and saponin constituents (Birhane et al., 2014). Flavonoids exert anti-inflammatory via scavenging reactive oxygen species (ROS) and reducing pro-inflammatory cytokines (e.g., nuclear factor-kappa B (NF-?B), TNF-?, IL-1?, and interleukin -6 (IL-6) (Singh et al., 2013; Sangeetha, 2015; Tadiwos et al., 2017).
The analgesic and anti-inflammatory activities of 80% methanol root extract and fractions might be due to the presence of phenols, tannins, saponins, terpenoids and flavonoids.

6. Conclusion and Recommendation
Crude methanolic extract, aqueous and butanol fractions of C. ficifolius proved to have analgesic properties against thermal, chemical noxious stimuli pain models; and anti-inflammatory in carrageenan induced paw edema. The crude extract and solvent fractions possess peripheral and central analgesic activity. The mechanism of anti-inflammatory actions may involve a multitude of inflammatory mediators.