This 2020 Chinese study compared the contents of 3, 5, and 7-day-old broccoli sprouts:

“The objective of this study was:

1. To optimize the extraction conditions of SF [sulforaphane] from seeds and sprouts at the same time to ensure the maximum SF yields from them;
2. To compare the SF yields, total flavonoid (TF) contents, and total phenolic (TP) contents from broccoli seeds and sprouts (after 3, 5, and 7 days germination respectively) of six different cultivated varieties; and
3. To evaluate and compare the the stability and bioaccessibility of SF, TF and TP from broccoli seeds and sprouts upon in vitro gastrointestinal digestion; total antioxidant activities of samples before and after digestion were also investigated in this section.

Most varieties obtained the maximum SF, TP and TF contents in sprouts on day 3. SF contents in sprouts were 46% – 97% of seeds, whereas TP and TF contents in sprouts were 1.12 – 3.58 times higher than seeds among varieties.

After in vitro digestion, broccoli sprouts from MNL variety kept considerable SF, TF, and TP contents, as well as antioxidant capacities, with all values higher than seeds.

SF from seeds and sprouts both showed high bioaccessibility values of 0.91 and 1.00, respectively. The high bioaccessibility of SF in vitro experiments provide an additional evidence for its efficient utilization, as many previous researches have reported a high bioavailability of SF in vivo.”

---

This study provided higher measures of sulforaphane in vitro bioaccessibility compared with previous studies of in vivo bioavailability.

It was good to read a definitive study that addressed both broccoli sprout age and cultivated variety for optimizing sulforaphane. The need was there. As the study authors put it:

“From the perspective of comparison methods, broccoli varieties, and germination processes, there is still lack of a systematic comparison of SF yields and other bioactive compounds contents between broccoli seeds and sprouts.”

https://www.sciencedirect.com/science/article/pii/S0308814620300637 “Sulforaphane and its antioxidative effects in broccoli seeds and sprouts of different cultivars” (not freely available)