## 3 Results  
### Histopathology and Ultra-Structural Studies  
The histo-architecture of the _C. carpio_ liver displayed hepatocytes with central nucleus and interspersed blood spaces (sinusoids) under light microscope (Figure 1A). Further, TEM of the liver detailed the central nucleolus in the nucleus, enclosed by the nuclear membrane extending into RER, and the marked presence of rod to ovoid shaped mitochondria (Figure 1B). Space of Disse, space amid the hepatocyte and sinusoids were evident with investing microvilli from the hepatocyte (Figure 1C). Bile canaliculi (BC) were lined with dense microvilli and apparent GC cisterns in its vicinity. Ample glycogen content was also found (Figure 1D). MG exposed _C. carpio_ evidenced erythrocytes infiltration, pyknotic and hypertrophic cells under light microscope (Figure 2A). Concomitantly, TEM studies displayed MG-induced karyological alterations such as pyknosis and organelle deformations including the loss of mitochondrion cristae and RER fragmentation (Figure 2B). Bile canaliculi showed membrane whorls and phagosomes in the vicinity (Figure 2C), indicating hampered cellular morphology and physiology. Instead, the amelioration (MG + EO) assay of 15 days histologically revealed the presence of pyknotic nuclei (Figure 2F). EO-induced defense system was evident with ultra-structural findings of the marked presence of macrophage cell and digested organelles in phage-lysosomes in the hepatocytes (Figure 2G,H). Histo-pathological study made in fish of group III, EO supplemented, showed a hepatocyte structure similar to the control (Figure 2E); however, the electron-micrograph also documented proliferated RER in the hepatocytes (Figure 2D). Figure 1: Hepato-architecture of control _C. carpio_. (**A**) (10\(\times\)): Liver with sinusoid (S). (**B**): Hepatocyte (H) showing central nucleolus (Nu), spherical nucleus (N) enclosed in nuclear membrane (Nm) and extended into RER, spherical to oval mitochondria (M) and abundant glycogen (GY) molecules. (**C**): Space of Disse (D) present between hepatocytes (H) and sinusoid (S), bearing erythrocyte (E) enclosed within fenestrated endothelium (fE). Microvilli (Mi) radiate in the space between. (**D**): Bile canaliculi (BC) with irradiating microvilli (Mi) and cisterns of Golgi complex (GC). Figure 2: Alterations in hepato-architecture of _C. carpio_ after exposure to malachite green and _E. officinalis_ for 15 days. MG: (**A**) (10\(\times\))—Liver with congested vessel (eV), pyknotic nucleus (Py), Hepaton pancreas (HP) and hypertrophied erythrocytes (HTE). (**B**): Pyknotic nuclei (Py), fragmented RER (fRER), rGY—reduced glycogen content. (**C**): Swollen mitochondrion (sM), phagosomes (Ph) and membrane whorls (Mw) in Bile canaliculi. _E. officinalis_: (**D**): Parallel arrangement of copious RER. (**E**) (40\(\times\))—Hepatocytes (H) with interspersed sinusoids (S). MG + _E. officinalis_: (**F**) (40\(\times\))—Pyknotic nuclei (Py) in polygonal hepatocytes (H). (**G**): Macrophage (Mc) with lysosomes (Ly) and heterochromatin (Hc) nucleus, central nucleolus (Nu) in spherical nucleus and presence of lipid inclusion (L); (**H**): numerous phagocytic vesicles, phagolysosomes (pLy), mitochondria and glycogen content. Chronic (30 days) exposure of MG in fish resulted in the appearance of prominent nuclear alterations and hypertrophied cells with congested vessels in hepatic tissue (Figure 3A). Cytological study made through TEM detailed distorted nuclear shape, lipid inclusions and conspicuous macrophage cells with numerous phagosome bodies (Figure 3C). Bile canaliculi exhibited the occurrence of membrane whorls and a reduced number of microvilli (Figure 3B). Significant depletion of the liver glycogen content was observed in MG intoxicated fish. The amelioration of MG toxicity with _E. officinalis_ resulted in inhibited alterations, and furthermore displayed erythrocyte infiltration (Figure 3F). Ultra-structurally, hepatocytes showed clumped mitochondria and numerous RER strands in the cytoplasm (Figure 3G).