Occurrence and new procedure of preparation of nigrin, an antiribosomal lectin present in elderberry bark

Elderberry (Sambucus nigra L.) is a food and medicinal plant which contains some lectins including nigrin which is a ribosome-inactivating protein. We search for the best source of nigrin and we develop an improved new method for isolation of nigrin based on ion-exchange and gel filtration chromatography instead of the affinity chromatography. Size and subunit composition and linking, and functional features like protein synthesis inhibition, N-glycosidase activity and cell viability inhibition, together with the stability of nigrin under simulated gastric digestion were studied. It has been found that nigrin accumulated into the secondary bark of spring and summer plants. The improved procedure is easily scalable and involves a first step of acidification followed by SP-Sepharose ion-exchange chromatography and finally a Sephacryl S-100 gel filtration yielding 0. 44 mg/g of wet elderberry bark. Nigrin prepared in that way retains all properties and upon intraperitoneal injection displays specific toxicity on intestinal crypts of APC/Min mice.

Research highlights
► We isolate the type 2 RIP nigrin by ion-exchange and gel filtration chromatography.
► Nigrin accumulates into the secondary bark of Sambucus nigra in spring and summer.
► Nigrin displays lower affinity for d-galactose-containing matrix than ricin.
► Nigrin displays specific toxicity on intestinal crypts of APC/Min mice.
► Nigrin is resistant to pepsin digestion at pH 1.5.