**1. Introduction**

In the dietary structure of honeybees, honey and bee pollen are the main food sources. Honey is the primary source of carbohydrates, whereas bee pollen can provide a variety of nutrients for growth and development, including proteins, carbohydrates, lipids, vitamins, and minerals [1]. These substances provide bee pollen with nutritional and medical properties, such as antibacterial, antioxidant, and immunoenhancement activities [2]. Bee pollen is also an important source of proteins and lipids for production of royal jelly [3], a viscous, milky substance that is secreted by honeybee hypopharyngeal and maxillary glands. It is nutrient-rich, containing substances such as proteins, amino acids, organic acids, lipids, and minerals [4]. Royal jelly not only promotes the growth and development of queen bee larvae, prolongs the honeybee lifespan [5], benefits animal reproduction and breeding [6], but it can also serve as a human functional food and dietary supplement, and is therefore of great significance in human healthcare.

In recent years, many studies have been conducted on the nutritional components and functional activities of royal jelly. The active substances in royal jelly (such as proteins, peptides, and lipids) can endow it with various functional activities, including anti-microbial,

**Citation:** Zhou, E.; Wang, Q.; Li, X.; Zhu, D.; Niu, Q.; Li, Q.; Wu, L. Effects of Bee Pollen Derived from *Acer mono* Maxim. or *Phellodendron amurense* Rupr. on the Lipid Composition of Royal Jelly Secreted by Honeybees. *Foods* **2023**, *12*, 625. https://doi.org/ 10.3390/foods12030625

Academic Editor: Vladimir Tomovi´c

Received: 6 December 2022 Revised: 13 January 2023 Accepted: 20 January 2023 Published: 2 February 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

anti-oxidative, anti-aging, anti-inflammatory, and hypoglycemic activities [7,8]. Lipids are small molecules that play important roles in maintaining the physiological dynamic balance. The LIPID MAPS database classifies lipids into eight categories, such as glycerolipids (GLs), glycerophospholipids (GPs), and sphingolipids (SPs) [9]. Royal jelly is rich in lipids, which account for 4–8% of fresh royal jelly and up to 15–30% of freeze-dried royal jelly products [3]. Free fatty acids (FAs) comprise ~90% of royal jelly lipids, which are of great significance to honeybee colonies. They not only provide nutrition for the queen and larvae during the developmental period, but also have antibacterial and mite repelling functions [10,11]. The free FAs in royal jelly also have various health-promoting activities and can be used as preventive and supplemental drugs for human health. Studies have shown that the lipid components of royal jelly can inhibit tumor cells, regulate the human immune system, prevent skin aging, and induce neurogenesis [12]. It is necessary to study the lipid composition of royal jelly to promote its development and utilization in human health applications.

The lipids in royal jelly are derived from the bee pollen consumed by honeybees. The lipid content of bee pollen is up to 13% of the dry weight, and the types and levels of lipids in bee pollen vary based on the plant source [13]. Importantly, it has been shown that the type of plant from which bee pollen is produced affects the lipid composition of royal jelly [5]. However, there has been a limited number of studies related to the effects of bee pollen consumption on the lipid composition of royal jelly. The traditional Chinese herbs *Acer mono* Maxim. and *Phellodendron amurense* Rupr. have a wide range of biological activities, including anti-oxidant, anti-tumor, anti-microbial, anti-inflammatory, anti-diabetic, and hepatoprotective effects [14,15]. Bee pollen derived from *A. mono* Maxim. (BP-Am) and from *P. amurense* Rupr. (BP-Pa) also retain these nutritional and pharmacological properties. However, the effects of BP-Am and BP-Pa consumption on royal jelly lipid composition have not been clarified.

We speculated that different plant source of bee pollen and different feeding time would significantly affect the lipid composition in royal jelly. Lipidomics technology has been widely used to identify the lipid composition in various foods and biological samples [16]. In this study, we applied a lipidomics approach to investigate the effects of two types of bee pollen (BP-Am and BP-Pa) on the lipid composition of royal jelly. Royal jelly secreted by honeybees with a natural mixed bee pollen diet was used as the control. We conducted analyses of royal jelly collected at several time points to determine changes in lipid composition during different stages of bee pollen consumption. An ultra-high performance liquid chromatography (UPLC)-Q-Exactive Orbitrap mass spectrometer was used to identify and quantify lipids in royal jelly samples. Our findings would provide guidance for the selection of the optimal feed for honeybees for the production of highquality royal jelly.
