Horseradish is a plant of the Brassicaceae family, which includes mustard and cabbages. The horseradish plant is to Europe and western Asia, but is now a popular herb around the world. Horseradish grows up to 4 feet tall and is mainly cultivated for its large white, tapering root, although the leaves are also edible.

The Horseradish root is used as a vegetable or ground in a condiment. Horseradish, sometimes blended with cream and called horseradish sauce, is often served with roast or boiled beef or sausages, as well as smoked fish. Horseradish is also used in some prepared mustards.

Wasabi and horseradish
Wasabi is often horseradish dyed green, but I have come across a study, see below, that gives wasabi a different species name. At this point I am not sure whether the wasabi in Japanese restaurants is basically horseradish dyed green, or wasabi plant from Japan.

Horseradish sauce ingredients

Horseradish sauce is usually made with fresh, grated orseradish, lemon juice, vinegar, sugar, mustard and heavy cream.

Infection, anti-bacterial
Biocontrol Sci. 2013. Antimicrobial activity of isothiocyanates (ITCs) extracted from horseradish (Armoracia rusticana) root against oral microorganisms. The antimicrobial activity of isothiocyanates (ITCs) extracted from horseradish root was investigated against oral microorganisms: 6 strains of facultative anaerobic bacteria, Streptococcus mutans, Streptococcus sobrinus, Lactobacillus casei, Staphylococcus aureus, Enterococcus faecalis and Aggregatibacter actinomycetemcomitans; one strain of yeast, Candida albicans, and 3 strains of anaerobic bacteria, Fusobacterium nucleatum, Prevotella nigrescens, and Clostridium perfringens. The ITCs extracted from horseradish root showed antimicrobial activity against all oral microorganisms by the paper disk method. The minimum bactericidal concentration (MBC) of the ITCs extracted from horseradish root ranged from 1.25 to 5.00 mg/ml against 6 strains of facultative anaerobic bacteria and one strain of yeast, and 4.17 to 16.67 mg/ml against 3 strains of anaerobic bacteria. The ITCs extracted from horseradish root showed the strongest antimicrobial activity, with a MBC of 1.25 mg/ml, against C. albicans among facultative microorganisms, and 4.17 mg/ml against F. nucleatum among anaerobic bacteria. These results suggest that the ITCs extracted from horseradish root may be a candidate for use as an antimicrobial agent against oral microorganisms.
 

Horseradish Research
Tumor cell proliferation and cyclooxygenase inhibitory constituents in horseradish (Armoracia rusticana) and Wasabi (Wasabia japonica).
J Agric Food Chem. 2005. Weil MJ, Nair MG. Bioactive Natural Products and Phytoceuticals, Department of Horticulture and National Food Safety and Toxicology Center, Michigan State University, East Lansing, Michigan
Cyclooxygenase and human tumor cell growth inhibitory extracts of horseradish (Armoracia rusticana) and wasabi (Wasabia japonica) rhizomes upon purification yielded active compounds 1-3 from horseradish and 4 and 5 from wasabi rhizomes. Spectroscopic analyses confirmed the identities of these active compounds as plastoquinone-9, 6-O-acyl-beta-d-glucosyl-beta-sitosterol (2), 1,2-dilinolenoyl-3-galactosylglycerol (3), linolenoyloleoyl-3-beta-galactosylglycerol (4), and 1,2-dipalmitoyl-3-beta-galactosylglycerol (5). 3-Acyl-sitosterols, sinigrin, gluconasturtiin, and phosphatidylcholines isolated from horseradish and alpha-tocopherol and ubiquinone-10 from wasabi rhizomes isolated were inactive in our assays. At a concentration of 60 microg/mL, compounds 1 and 2 selectively inhibited COX-1 enzyme by 28 and 32%, respectively. Compounds 3, 4, and 5 gave 75, 42, and 47% inhibition of COX-1 enzyme, respectively, at a concentration of 250 microg/mL. In a dose response study, compound 3 inhibited the proliferation of colon cancer cells (HCT-116) by 21, 42, 51, and 68% and lung cancer cells (NCI-H460) by 30, 39, 44, and 71% at concentrations of 7, 15, 30, and 60 microg/mL, respectively. At a concentration of 60 microg/mL, compound 4 inhibited the growth of colon, lung, and stomach cancer cells by 28, 17, and 44%, respectively. This is the first report of the COX-1 enzyme and cancer cell growth inhibitory monogalactosyl diacylglycerides from wasabi and horseradish rhizomes.