ETHNOBOTANY, PHYTOCHEMISTRY AND PHARMACOLOGY OF OCHNA SCHWEINFURTHIANA : A REVIEW

Ochna schweinfurthiana ( Os , Family: Ochnaceae) is a small evergreen tree used in ethnomedicine to treat different ailments; it is also used in agri-horticulture and as ornaments, dyes among others. Chemical investigations conducted on the different parts of the plant have been confined to phenolic compounds majorly bioflavonoids, glycosides, steroids and terpenes. The plant, Os have shown a wide spectrum of biological and pharmacological properties which include antimicrobial, anti-inflammatory, antioxidant and antiplasmodial. This review comprehensively summarize the potential effects of the plant Os chemically and pharmacologically ( in vitro and in vivo ). However, more researches in the aspect of phytochemical and biological studies are needed to exhaustively isolate bioactive compounds and evaluate their effects on other ailments as claimed by the traditional healers.


Introduction
Ochna schweinfurthiana (Os)belonging to the Ochnaceaefamily is a small tree that was named after a German botanical collector and taxonomist Dr. Georg August Schweinfurth; it is an attractive tropical small tree that measures up to 4 m tall and the plant is commonly known as the brick-red Ochna in English, Jan-taru in Hausa language, Hiéké in Yoruba and Sa'aboule in Foufouldé (Burkill, 1985;Messi et al., 2016).The plant can be used as medicine, for agricultural, social and religious purposes (Burkill, 1985). This review will focus on the phytochemical and pharmacological properties of Os.

Main text 2.1 Botanical Description
Ochna originated from a Greek word "Ochnewhich means wild pear". It was named by Linnaeus in 1951 as Ochna because of the resemblance of their leaves with those of wild pear (Muema, 2015). Itis an old world genus of mainly trees, shrubs and shrublets which comprises of about 85 species (Verdcourt, 2005) and it is widely distributed widely in tropical Asia, Africa and America (Rendle, 1952) of which eleven (11) species occur in India (Kirtikar, 2012). Ochna's are usually called Mickey Mouse plants, as a result of the appearance of their black druplets fruits sitting.The Ochnaceaefamily is mainly comprised of trees and shrubs with about 33 genera and 550 species (Christenhusz and Byng, 2016) which are highly distributed around the globe; the species are mostly found in Tropical Africa, Asia, Australia, Madagascar, the Mascarene island and America (Mabberley, 2008). They are notably known for their unusual leaves that are shiny, with closely spaced, parallel veins, toothed margins, and conspicuous stipules (Burkill, 1985;Christenhusz and Byng, 2016). The largest genera are Ouratea, Ochna,Campylospermum,SauvagesiaandQuiinawith(200,85,65,39 and 34 species) respectively (Table 1).  3. Uses 3.1 Ethnomedicinal uses Several preparations (powdered and decoction) of the leaves and/or root of the Os have found a general use as an antimicrobial (wound dressing, eye infection), analgesic, anti-inflammatory and anthelmintic agents (Burkill, 1985). The leaf is also used as a laxative, enema, febrifuge, antiseptic, stimulant, among others (Burkill, 1985). In Northern Cameroon, Os is used to treat Comment [D19]: Please mention these are original or copied from other published literature. If copied, is there any approval to use these images? different metabolic diseases such as rubella, burns, stomachache and multiple sclerosis (Abdullahi et al., 2010); the root of the plant is also used to treat headache, stomach and eye aches while the leaves are used in the treatment of toothaches (Messiet al., 2016). The powdered bark is used as antimalarial, febrifuges and anthelminthic, while the decoction of the root, leaves or bark is used in dressing wounds (Abdullahi et al., 2010). In Northern Nigeria, the plant is used for the treatment of measles, typhoid fever and fungal skin infections (Abdullahi et al., 2010). The macerated roots of Os has been reportedly used to induce/speed the delivery process and for miscarriage (Bruschiet al., 2011).

Other uses
The plant is used in agri-horticulture; the bark and flowers Osare cultivated for ornaments, dyes, stains, inks, tattoos and mordent among others. The wood is used for farming, forestry, hunting and fishing apparatus. The leaf has social, religious, superstitious and magic values among others (Burkill, 1985). Abdullahi et al.(2010)reported the presence of flavonoids, steroids/terpenes and saponins in the acetone leaf extract of Os and the methanol leaf extract indicated the presence of flavonoids and saponins. However, flavonoids, saponins, glycosides, tannins and steroids/terpenes were reported on the methanol stem extract of Os (Danmusaet al., 2015).A study conducted by Ibrahim et al. (2015) reported the presence of carbohydrates, steroids/triterpenes, glycosides, saponins, tannins and flavonoids in the methanol leaf extract of Os.

Genotoxicity
Djovaet al. (2019) reported that the extracts of Oswere nongenotoxic in a study he carried out; this is because none of the plant extracts demonstrated a dose dependent increase or revertent colonies ≥ the number of negative control revertent colonies; thus, the plantOs is devoid of any genotoxic substances that can lead to mutations either by substitution or by reversion in the genetic material.

Antinoceptive and Anti-inflammatoryeffect
The methanol leaf extract of Os significantly inhibited the writhing response induced by acetic acid in a dose dependent manner; the highest dose exhibited maximum inhibition of pain (84.3 %). In addition, the extract was also able to attenuate pain response in a similar manner though with a slower onset of action in the tail flick model (Ibrahim et al., 2015a). The aqueous bark extract of Os exhibited good anti-inflammatory effect in both ferrous oxidation-Xylenol Orange (Fox) and BSA denaturation assays; the extract demonstrated good 15-lipoxygenase inhibitory effect with an IC 50 value of 32.2±0.36µg/mL, however, an IC 50 of 130±5.78µg/mL was recorded by the extract in the inhibition of heat induced albumin denaturation (Djovaet al., 2019).

Antiplasmodial effect
An in vivo study showed that the methanol leaf extract of Osexerted a suppressive effect against Plasmodium berghei at a lower dose (50 mg/kg); Ibrahim et al. (2015b) concluded that, the ability of the extract to suppress malaria at the early stage is an indication that, it possess blood schizonticidal activity. Moreso, the extract reduced the level of parasitaemia with 100 % cure at the lowest dose (50 mg/kg); the percentage inhibition of parasitaemia was higher than the chemo suppression due to non-selectivity of the extract to the proliferative process of the parasite (Salawuet al., 2010;Ibrahim et al., 2015b).
Antiplasmodial effect of the ethylacetate roots extract of Os and some compounds 4'''methoxylophirone glucopyranosyl-2,9-dihydroxyhexeicosa-4,7-diene (15), calodenine B (17), lophirone A (18) and gerontoisoflavone A (19) were investigated in vitro; 4''-methoxylophirone A (13) showed good antiplasmodial effect against Plasmodium falciparum strain 3D7; this effect as explained by Messiet al. (2016) might be related to the presence of a methoxy group on position C-4''' which has been known to enhance lipophilicity thereby enhancing its movement into the cells (Monks et al., 2002); other compounds were inactive (Messiet al., 2016). Cold and hot aqueous leaf extracts of Os possess inhibitory effect against P. falciparum in vitro; thus there was significant reduction of parasitaemia. The high dose (80 µg/mL) exhibited 86.42 % (cold extract) and 85.06 % (hot extract) reduction of parasitaemia. On the other hand, no any significant difference was observed on the plasmodium lactate dehydrogenase ( P LDH) activity of the treated extract when compared with the standard drug (Omoniwa, 2017).

Toxicity
Toxicity level of Os was assessed in mice both orally and intraperitoneally. The methanol leaf extract of the plant produced an LD 50 774.6 mg/kg, i. p. while the oral LD 50 value for the extract was 5000 mg/kg; according to this study, the plant is toxic intraperitoneally and safe orally (Ibrahim et al., 2015b).

Conclusion
Os exhibit a variety of biological effects; the plant is considered to be effective against cancer, malaria, oxidative stress, pain, inflammation and a wide range of microbes; thus, the pharmacological actions have been attributed to the presence of different classes of secondary metabolites such as biflavonoids, glycosides, steroids and terpenes among other. In addition, the mechanism of action of the observed effects and evaluation of other pharmacological properties of Os still need attention and it should be the objective of new researches on Os.