Which one of the following causes Melanosis coli?

(B) Senna[?]Melanosis coli is dark brown pigmentation of the colonic mucosa that occurs with the long term use (at least 4-9 months) of stimulant or irritant laxatives containing anthraquinone, such as senna, aloe, cascara, rhubarb.oThe condition is benign and reversible on discontinuation of the laxative.oAnthraquinone laxatives act by producing massive migrating colonic contractions and induce water and electrolyte secretion.oAnthraquinones have a direct toxic effect on the epithelial cells of the colon that results in the production of lipofuscin, the dark pigment seen in macrophages in melanosis coli.oThe cecum and rectum are the most common sites of melanosis coli, but it can affect the entire large bowel.oHistological, this is caused by the presence of pigment laden macrophages within the lamina propria.oThese agents also have been associated with the development of "cathartic colon", which can be seen in patients (typically women) on long term use.oThese compounds are excreted in the bile, saliva, milk, and urine.oChrysophandic acid, a component of senna and rhubarb color acidic urine yellowish brown and alkaline urine reddish violet (should warn patients)oProlonged use may cause watery diarrhoea with excess loss of fluid and electrolytes particularly potassium, muscle weakness and weight loss.oChanges in the intestinal musculature associated with malabsorption and dilation of the bowel, similar to ulcerative colitis and to megacolon, may also occur.oCardiac & renal symptoms have been reported. Other Options[?]Bisacodyl:oBisacodyl is a stimulant purgative.oBisacodyl is activated in the intestine by deacetylation.oTheir primary site of action is in the colon: irritate the mucosa, produce mild inflammation and secretion.oOne or two semiformed motions occur after 6-8 hours.[?]Magnesium sulfate:oMag. sulfate (Epsom salt): 5-15 g; bitter in taste.oMag. salts are contraindicated in renal insufficiency, while Sod. salts should not be given to patients of CHF and other Sod. retaining states. Repeated use of saline purgatives can cause fluid and electrolyte imbalance.oThey are practically not used for the treatment of constipation, because after constipation is quite common.oHowever, they may be preferred for preparation of bowel before surgery and colonoscopy; in food/ drug poisoning and as after-purge in treatment of tapeworm infestation.[?]Lactulose:oLactulose It is a semi synthetic disaccharide of fructose and lactose which is neither digested nor absorbed in the small intestine-retains water.oFurther, it is broken down in the colon by bacteria to osmotically more active products.oLactulose causes reduction of blood NH3 concentration by 25-50% in patients with hepatic encephalopathy.