The present study aimed to elucidate the negative impacts of UVA on some biochemical and hematological
variables of the economically important African catfish, Clarias gariepinus and investigates the putative
role of quince (Cydonia oblonga Miller) leaf extract in protection and/or alleviation of such negative
impacts. Changes in the hematological and blood biochemical values often reflect alteration of physiological
state. Blood parameters can be useful for the measurement of physiological disturbances in stressed
fish and thus provide information about the level of damage in the fish. We found a significant (P < 0.05)
decrease in the red blood cell counts, hemoglobin and hematocrit in the groups exposed to UVA compared
to the control groups. Exposure to UVA induced marked red cell shrinkage (increased mean cell
hemoglobin concentration) and showed an elevation in mean cell volume and mean cell hemoglobin
in the blood of the exposed fish compared to the control. A significant (P < 0.05) reduction in the total
white blood cells was recorded in the exposed fish compared to the control. The biochemical parameters
(blood glucose, total plasma protein, blood cholesterol, plasma creatinine, aspartic amino transferase and
alanine amino transferase) exhibited a significant increase in the blood of fish exposed to UVA.
Methanolic extract of quince leaf before ripening of the fruits was analyzed by GC/MS. To investigate
the biological impact of this extract and its biologically active components, this extract was tested for
its putative role in alleviation of UVA effect on catfish. Quince leaf extract had the ability to prevent
hematotoxic stress induced by UVA and resulted in enhancement of the immune system of catfish represented
by significant (P < 0.05) increase in the number of white blood cells and lymphocytes of the catfish.
Quince extract also protected the red blood cells from UVA damage. To our knowledge this is the first
report of the effect of quince leaf extract on an aquatic organism.