Effect of meal composition and cooking duration on the fate of sulforaphane following consumption of broccoli by healthy human subjects

Abstract

The isothiocyanate, sulforaphane, has been implicated in the cancer-protective effects of brassica vegetables. When broccoli is consumed, sulforaphane is released from hydrolysis of glucoraphanin by plant myrosinase and/or colonic microbiota. The influence of meal composition and broccoli-cooking duration on isothiocyanate uptake was investigated in a designed experiment. Volunteers (n 12) were each offered a meal, with or without beef, together with 150 g lightly cooked broccoli (microwaved 2·0 min) or fully cooked broccoli (microwaved 5·5 min), or a broccoli seed extract. They received 3 g mustard containing pre-formed allyl isothiocyanate (AITC) with each meal. Urinary output of allyl (AMA) and sulforaphane (SFMA) mercapturic acids, the biomarkers of production of AITC and sulforaphane respectively, were measured for 24 h after meal consumption. The estimated yield of sulforaphane in vivo was about 3-fold higher after consumption of lightly cooked broccoli than fully cooked broccoli. Absorption of AITC from mustard was about 1·3-fold higher following consumption of the meat-containing meal compared with the non meat-containing alternative. The meal matrix did not significantly influence the hydrolysis of glucoraphanin and its excretion as SFMA from broccoli. Isothiocyanates may interact with the meal matrix to a greater extent if they are ingested pre-formed rather than after their production from hydrolysis of glucosinolates in vivo. The main influence on the production of isothiocyanates in vivo is the way in which brassica vegetables are cooked, rather than the effect of the meal matrix.

Effect of cooking brassica vegetables on the subsequent hydrolysis and metabolic fate of glucosinolates

“…However, the fat content of the meatcontaining meal was shown to be five times higher than that of the vegetarian meal and may have facilitated the absorption of pre-formed isothiocyanates, which are relatively hydrophobic. Inter-individual variations of £ 4-fold in total sulforaphane MA output, similar to the variation reported by Getahun & Chung (1999) after consuming cooked watercress, has been observed (Rungapamestry et al 2007) after the intake of cooked broccoli. The main influence on the absorption of isothiocyanates in vivo is the way in which brassica is cooked, rather than the effect of the meal matrix.…”

“…In one study (Rungapamestry et al 2007) the absorption of sulforaphane following consumption of 150 g lightlycooked (microwaved for 2 min) or fully-cooked (microwaved for 5 . 5 min) broccoli, containing glucoraphanin, along with a meat-containing meal or its vegetarian alternative has been investigated in twelve human volunteers.…”

The role of phytochemicals in modulating intrinsic human cellular defence processes

“…confirm the necessity for MYR in optimising SFN Yield, citing cooking and extraction as being the primary processes leading to loss of activity. 424,245,399 The SFN bioavailability 399 from raw broccoli was shown to be 10-fold higher than for cooked broccoli. Plasma SFN peaked at about 1.6 hours after ingesting raw broccoli but peaked later at around six hours after cooked broccoli.…”

“…244 Cooking and especially prolonged cooking denatures the enzyme. 245,246 It becomes clear that for cruciferous vegetables to retain their bioactivity and maintain their efficacy, they must be handled carefully and with thorough understanding of the factors associated with their degradation. 247,248 MYR activity from broccoli vegetable has been reported to be thermolabile, with loss of approximately 90% activity after only 2 minutes of microwave cooking.…”

“…37,38,41,197,245,318,[383][384][385][397][398][399]412,[424][425][426][427][428][429][430][431][432] These materials include mature broccoli vegetable (raw and cooked), fresh broccoli sprouts, MYR-inactive broccoli extract beverage, MYR-inactive powdered broccoli sprout extract (BSE), MYR-active broccoli sprout powder and capsules made from MYRinactive broccoli extract. Several of the studies 38,397,398,430 confirm the necessity for MYR in optimising SFN Yield, citing cooking and extraction as being the primary processes leading to loss of activity.…”