Elderberries: a source of ribosome-inactivating proteins with lectin activity

Abstract

Sambucus (Adoxaceae) species have been used for both food and medicine purposes. Among these, Sambucus nigra L. (black elder), Sambucus ebulus L. (dwarf elder), and Sambucus sieboldiana L. are the most relevant species studied. Their use has been somewhat restricted due to the presence of bioactive proteins or/and low molecular weight compounds whose ingestion could trigger deleterious effects. Over the last few years, the chemical and pharmacological characteristics of Sambucus species have been investigated. Among the proteins present in Sambucus species both type 1, and type 2 ribosome-inactivating proteins (RIPs), and hololectins have been reported. The biological role played by these proteins remains unknown, although they are conjectured to be involved in defending plants against insect predators and viruses. These proteins might have an important impact on the nutritional characteristics and food safety of elderberries. Type 2 RIPs are able to interact with gut cells of insects and mammals triggering a number of specific and mostly unknown cell signals in the gut mucosa that could significantly affect animal physiology. In this paper, we describe all known RIPs that have been isolated to date from Sambucus species, and comment on their antiviral and entomotoxic effects, as well as their potential uses.

Figure 1

Effects of nigrin b on intestines. Histological sections of small (left) and large (right) intestine in mice six hours after injection with 16 mg/kg nigrin b. Lieberkühn’s crypts show atrophy due to increased apoptosis (arrows). (left) Semi-thin section stained with toluidine blue. ×1000; (right) Haematoxylin and eosin. ×500.

Figure 2

Electron micrograph of Lieberkühn’s crypt of the small intestine in a mouse 6 h after injection with 16 mg/kg nigrin b. Dead cells showing apoptotic bodies can be seen at the bottom of the crypt (arrows). ×5800.

Figure 3

Effects of ebulin f on intestines. Histological sections of small (left) and large (right) intestine of mice stained with haematoxylin and eosin. (left) Severe atrophy of Lieberkühn’s crypts (arrows) is present in an animal injected with 5 mg/kg. ×235; (right) Derangement of the epithelium showing some dead cells sloughed off in the colonic lumen (arrow) can be seen in an animal injected with 2.8 mg/kg ebulin f. ×180.