Efek antioksidan ekstrak bekatul oryza sativa varietas IPB-3S terhadap kadar malondialdehida mda otak tikus yang diinduksi karbon tetraklorida CCl4 = The antioxidant effects of oryza sativa variety IPB-3S rice bran extract towards malondialdehyde mda levels in rat brain induced by carbon tetrachloride CCl4