Subclass of Amino Acids & Proteins

Proteins & Peptides

Plant proteins and peptides, including enzymes and the ribosome-inactivating proteins.

Overview

About Proteins & Peptides

Proteins and peptides are chains of amino acids — peptides short, proteins long and folded into a defined three-dimensional shape. In a phytochemistry reference they occupy an awkward but interesting position, because their behaviour is governed by a constraint no small molecule faces.

That constraint is digestion. A protein taken by mouth is normally taken apart into amino acids before it can do anything, so any claim that a plant protein acts systemically after being swallowed needs to explain how it survived the stomach. Some genuinely do; most do not.

What Falls Under This Heading

Several quite different kinds of molecule share this page:

Lectins: carbohydrate-binding proteins: ricin, mistletoe viscotoxins, bean phytohaemagglutinin
Ribosome-inactivating proteins: trichosanthin, momorcharins, MAP30
Protease inhibitors: the Bowman-Birk and Kunitz families of legumes
Enzymes: bromelain from pineapple, papain from papaya, ficin
Cyclotides and small peptides: the cyclic peptides of Rubiaceae and Violaceae
Structural and storage proteins: the bulk by mass, and pharmacologically inert

Pharmacological Importance

The proteolytic enzymes are the clearest case of orally active plant proteins. Bromelain is absorbed intact in small but measurable quantities and has reasonable evidence in post-surgical swelling and osteoarthritis; both bromelain and papain are used as topical debriding agents, where digestion is not an obstacle at all.

The cyclotides are the structural curiosity worth knowing: their backbone is a closed circle stabilized by a knotted disulfide core, which makes them exceptionally resistant to heat and proteases — and an active scaffold in peptide drug design for precisely that reason. Mistletoe lectins are the basis of the injected mistletoe preparations used as adjunctive cancer therapy in parts of Europe.

Toxicity & Safety

This class contains the single most toxic compound in the plant kingdom. Ricin, the lectin of castor bean, inactivates ribosomes catalytically — a handful of molecules can kill a cell, and a few seeds can kill a person.

Less dramatically, undercooked kidney beans cause acute vomiting and diarrhoea through phytohaemagglutinin, which is destroyed by proper boiling but not by slow cooking at low temperature. Plant proteins are also the main route to true IgE-mediated food allergy — the peanut, soy and tree-nut allergens are proteins — and the proteolytic enzymes are recognized occupational sensitizers.

Constituents

All Proteins & Peptides

63 total Filter proteins & peptides

Adenoregulin Agglutinins 1 herb Albuminoids 1 herb Alpha-amanitin 2 herbs Alpha-momorcharin 1 herb Amanin Amaninamide Amatoxin Amphomycin Angiotensin amide

Beta-amanitin 2 herbs Beta-momorcharin 1 herb BG-4 1 herb Bombesin Bombesinnona peptides Bradykinin derivatives

Caerulein Capreomycin Ciclosporin collagen 1 supp Concanavalin A 1 herb Corticotrophin

Deltorphin Deltorphins

Open in filterable index

Source Plants

Herbs Containing Proteins & Peptides

13 herbs

Plants in the materia medica documented to carry proteins & peptides, with the compounds each one is listed for. The bar counts how many DISTINCT proteins & peptides are on record for a plant, relative to the best-documented — it measures breadth of record, not potency, so a plant with one well-studied compound can outrank a richer source that has simply been analysed less. No concentration figures are on record for this class yet, so nothing here distinguishes a major source from a trace.