Neuroprotective effects of ethanol extract of Ocimum gratissimum leaf on monosodium glutamate-induced oxidative stress in developing Wistar rat cerebellum

Authors

  • Dr. I.O. Imosemi

Abstract

Background: The safety of monosodium glutamate (MSG) as a flavour enhancer has generated much controversy. This research investigated the neuroprotective effect of ethanolic leaf extract of Ocimum  (OG) against MSG-induced oxidative stress in developing Wistar rat brains. Methods: Thirty pregnant rats were divided randomly into six groups of five animals per group. Control; MSG (4 g/kg); MSG + Vitamin E (500 mg/kg); OG (300 mg/kg dissolved in corn oil) + MSG; OG; Corn oil, CO (vehicle). The pregnant rats received oral administration from day 7 of gestation to postnatal day 28, while the pups received oral administration from the 21st to the 28th postnatal day. Behavioural test was done on day 21 and the pups were killed. The cerebella of pups of days 1, 7, 14, 21 and 28 were dissected out for histological and histomorphometric studies, while biochemical evaluation was done on day 21postpartum.

Results: In the behavioural assessment (open field test), only the rats in the MSG + Vit. E (5.00±1.41) and CO (4.75±1.50) groups showed a significant reduction at p<0.05 compared to the control (19.00±8.71) in longitudinal movement and number of grid lines crossed with four paws within five minutes. Rats in all the treatment groups showed a reduced tendency for rearing compared with the control group at p<0.05. Biochemical analysis showed a decreased glutathione (GSH) and glutathione peroxidase (GSH-Px) activity in the MSG group compared with the control pups, and that OG significantly (P<0.05) increased the GSH and GHS-Px activity compared with MSG animals. Superoxide dismutase (SOD) activity was significantly increased in the control and OG+MSG rats compared with the MSG, OG, MSG + Vit E and cornoil groups at p<0.05. Histological alterations were minimal, with a thicker external granular layer seen in the MSG and MSG+Vit E pups on day 14, and decrwased molecular layer thickness on day 28.

Conclusion: These results suggest that the adverse effects of MSG are mild and OG possesses bioactive phytochemicals capable of preventing and/or reversing MSG-induced oxidative stress. Further studies are recommended to clearly define the mechanism of OG action

Keywords: Ocimum gratissimum, monosodium glutamate, oxidative stress, developing cerebellum, neuroprotection

Résumé
Contexte: La sécurité du glutamate mono-sodique (MSG) comme stimulateur de saveur a suscité beaucoup de controverse. Cette recherche a étudié l’effet neuro-protecteur de l’extrait éthanoïque de feuilles d’Ocimum gratissimum (OG) contre le stress oxydatif induit par MSG dans le développement des cerveaux de rats Wistar.

Méthodes: Trente rats en gestations ont été divisées de façon aléatoire en six groupes de cinq animaux par groupe. Contrôle; MSG (4 g / kg); MSG + vitamine E (500 mg / kg); OG (300 mg / kg dissous dans de l’huile de maïs) + MSG; OG; Huile de maïs (véhicule). Les rats en gestations ont reçu une administration par voie orale entre le jour 7 de la gestation et le jour 28 postnatal, tandis que les souriceaux ont reçu une administration orale du 21ème au 28ème jour postnatal. Le test de comportement a été effectué le jour 21 et les souriceaux ont été tués. Les cervelets des souriceaux du jour 1, 7, 14, 21 et 28 ont été disséqués pour les études histologiques et histomorphométriques, alors que l’évaluation biochimique a été effectuée le jour 21 après le départ.

Résultats: Dans l’évaluation comportementale (test en champ ouvert), seuls les rats du MSG + Vit. E (5,00 ± 1,41) et les groupes CO (4,75 ± 1,50) ont montré une réduction significative à p <0,05 par rapport au contrôle (19,00 ± 8,71) dans le mouvement longitudinal et le nombre de lignes de grille croisées avec quatre pattes dans les cinq minutes. Les rats dans tous les groupes de traitement ont montré une tendance réduite à l’élevage par rapport au groupe témoin à p <0,05. L’analyse biochimique a montré une activité diminuée de glutathion (GSH) et de glutathion peroxydase (GSH-Px) dans le groupe MSG par rapport  aux chats témoins et que OG a significativement (P <0,05) a augmenté l’activité GSH et GHS-Px par rapport aux animaux MSG. L’activité du super-oxyde dismutase (SOD) a été significativement augmentée dans le contrôle et les rats OG + MSG par rapport aux groupes MSG, OG, MSG + Vit E et control à p <0,05. Les altérations histologiques ont été minimes, avec une couche granulaire externe plus épaisse observée chez les souriceaux MSG et MSG + Vit E le jour 14 et une diminution de l’épaisseur de la couche moléculaire au jour 28.

Conclusion: Ces résultats suggèrent que les effets indésirables du MSG sont doux et le OG possède des phyto-chimiques bioactifs capables de prévenir et / ou inverser le stress oxydatif induit par MSG. D’autres études sont recommandées pour définir clairement le mécanisme de l’action OG

Mots-clés: Ocimum gratissimum, glutamate mono-sodique, stress oxydatif, développement du cervelet, neuro-protection

Correspondence: Dr. I.O. Imosemi, Department of Anatomy, College of Medicine, University of Ibadan, Ibadan, Nigeria. E-mail: innosemi@yahoo.co.uk

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Published

2020-09-02

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